Clinical Toxicology (CTX) Final Handout - 2023 PDF

Clinical Toxicology (CTX) 1 Introduction Toxic substance is any substance that can produce harmful effects on the living organisms. Diagnosis of poisoning The diagnosis in a case of poisoning can be made from the followings: 1) History. 2) Physical Examination....

Clinical Toxicology (CTX) 1 Introduction Toxic substance is any substance that can produce harmful effects on the living organisms. Diagnosis of poisoning The diagnosis in a case of poisoning can be made from the followings: 1) History. 2) Physical Examination. 3) Laboratory Evaluation. 4) Toxicological Screening. I-History: II. Clinical Picture: 1) Vital signs: a. B.P: systolic 100-140 and diastolic 60-90 b. Pulse: 60 - 90 beats per minute. c. Respiration: 12–16 breaths/minute d. Temperature: 36.5 -37.2 C 2) Complete general and local examinations: - a. Skin, smell of breath and pupils. b. Chest and abdomen examination. c. Neurological examination: Rapid assessment of mental status, pupil size, muscle tone, reflexes, skin. d. Identify toxic syndromes. Coma Coma is a state of unconsciousness in which a person cannot be awakened 2 Coma Scales: - Definitive Monitoring of Toxic Coma: For definitive monitoring of toxic coma, some prefer to use Reed's coma scale, and Glasgow coma scale (GCS). Glasgow coma scale is the most frequently used in the assessment of the degree of impaired consciousness. Reed's Coma Scale Glasgow Coma Scale The maximum score is 15 & the least is 3 with bad prognosis. 3-Labororatory evaluation: 4-Other investigations: Management Supportive care 1-Airways& Breathing (A, B): A. Keep Airway opened: 3  Indications for Intubation & Assisted ventilation: B. Breathing ( O2 therapy ) 2- Cardiovascular (CV):  Hypotensive patients→ intravenous infusion of normal saline, adrenaline, dopamine.  Hypertension →antihypertensive agents  Arrhythmia →antiarrhythmic drugs 3-Treat Coma (COMA COCKTAIL): 1. Dextrose: All comatose patients should receive concentrated dextrose unless hypoglycemia is excluded 2. Naloxone: 3. Thiamine: If Alcoholism or Malnutrition is suspected 4. Flumazenil, in case of suspected benzodiazepine poisoning. 4- Treat Seizures: 5- Search for associated illness: Look for cause of coma or seizures Prevention of absorption (GI decontamination & decontamination of other sites) I- Gastrointestinal Decontamination: (for ingested poisons) it includes:  Gastric emptying by emesis or gastric lavage.  Activated charcoal.  Cathartics & whole bowel irrigation A. Emesis It is induced with: Apomorphine: is a parenteral emetic and can be used with caution because of its CNS (stimulation of C.T.Z) and cardiac side effects.  Contraindications to the induction of emesis are: Patient Poison 1- CNS. Problems:- 1. Chronic poisoning a) Coma: fear of asphyxia & aspiration 2. Corrosives [Inorganic]:- fear pneumonia. of perforation b) Convulsions: as it may induce new attack of 3. Volatile hydrocarbons convulsion. [kerosene]: fear of aspiration 2-CVS diseases: [as it will cause electrolyte pneumonia. imbalance and effort on heart] 4. Poisons result in rapid onset of 3-GIT problems: CNS depression c) Varices [ as it will cause bleeding] Absent gag reflex and fear of aspiration pneumonia. a. Recent gastric operation. 4-Infants under 6 months (poor gag and air way protective reflexes 4  B. Gastric Lavage: Definition: Removal of the stomach contents by washing using a tube. Indications:  Recent ingestion of substances [Within 3 hrs post ingestion & emesis failed].  When patients are uncooperative or lethargic.  But it may be useful as long as 12 hrs post ingestion in some poisons as: 1. Poisons which stick to stomach 2. Poisons which slow down motility of stomach 3. Poisons which secreted in stomach Complications: 1. Aspiration pneumonia. 2. Esophageal perforation leads to mediastinitis & shock. 3. Bleeding. 4. Hypothermia: if cold solutions were used. 5. Cardiac arrest. 6. Psychic trauma. C. Activated Charcoal It has powerful adsorption capacity and is given orally or via gastric tube. It irreversibly binds the drugs within the bowel preventing its absorption. Substances Not Adsorbed By Activated Charcoal (CHARCOAL)  C: Corrosives, cyanide salts.  H: Heavy metals.  A: Alcohols and glycols.  R: Rapid onset or absorption as in cyanide and strychnine.  C: Chlorine , iodine.  O: organophosphorous.  A: Aliphatic hydrocarbons (kerosene).  L : Laxative (potassium) and Lithium. Advantages: 1. Administered very quickly if the patient is awake and cooperative. 2. Effective in cases with inaccurate history, and if the time of ingestion is unknown. 3. Adsorb most of the commonly ingested drugs and chemicals. 4. Can pass easily through pylorus (the primary site of drug absorption) unlike emesis and lavage. Disadvantages: 1. It may adsorb oral antidotes (N- acetylcysteine, penicillamine and DMSA) & prevent their actions. So, antidotes should be given after lapse of 1-2 hours. 5  2. It may induce vomiting (gritty texture, volume administration, additives as sorbitol or a combination of them all). 3. Mechanical obstruction of airways, if aspired into lungs. 4. Mechanical bowel obstruction in multiple dose manners especially with decreased gut motility. Contra-indications: 1- Caustic ingestion: a) Ineffective adsorption. b) May induce vomiting. c) Limitation of visual field during endoscopy. d) Induction of complications if perforation has occurred 2- Intestinal obstruction. 3- Absence of bowel sounds [a dynamic ileus]. 4- Lack of adequate airway protection e.g. coma. D. Multiple Dose Activated charcoal (MDAC) (GI Dialysis) Principle: MDAC facilitates the passage of toxin from plasma into intestine by creation of concentration gradient between blood and bowel fluid, this will enhance the efflux of toxin into intestinal lumen. Indications: for poisoning that: - Show enterohepatic circulation - Stick to the stomach - Slow gut motility E. Cathartics [Purgatives] They promote the rectal evacuation of gastrointestinal contents. Types: a) Osmotic cathartics: - Salts: MgSO4 - Sorbitol: Their aim is to prevent constipation following charcoal administration. b) Oil cathartics: Castor oil. Contraindications: Intestinal obstruction. Absence of bowel sounds. Pre-existing diarrhea with electrolyte disturbances. Mg-containing cathartics: should not be used in renal failure. Oil cathartics: May enhance absorption of fat-soluble poisons e.g. pesticides. Corrosive ingestions (may induce intestinal injury). 6  Complications: 1- Electrolyte imbalance. 2- Dehydration. F. Whole bowel irrigation It is performed by irrigation of the entire GIT with non-absorbable isotonic electrolyte solution containing Polyethylene Glycol, orally or by gastric tube until rectal effluent is clear. The patient must be in sitting position. Indications: Foreign bodies. Packets of illicit drugs. Slow releasing or enteric coated medicines. Heavy metals. Contraindication: 1. Patients with bowel obstruction. 2. Ileus. 3. Hemodynamic instability. 4. Compromised unprotected airway. 5. Electrolyte disturbance. Elimination of absorbed poisons (Forced diuresis, extracorporeal methods) (1) Forced diuresis and pH manipulations {ion trapping}: Aim: maintain urine output of 8-24 L/day by increasing renal blood flow. Method: a) Drugs (frusemide) b) Mannitol Indications: Drugs which are: a) Excreted by the kidney. b) With small volume of distribution. c) Small protein binding affinity. Ion trap: Since many toxins are weak acids or bases, they can be ionized in solutions of varying pH. In the Ionized state, they are less likely to cross cell membranes and their reabsorption by renal tubular epithelium is decreased. Types of ion trapping: 1. Alkalization of urine - For elimination of acidic drugs e.g. salicylates and barbiturates. - Using: (NaHCo3) → urine pH 7.5-8.0. 7  2. Acidification of urine - For elimination of alkaline drugs e.g. Amphetamine, (1) Contraindication to forced diuresis: 1. Heart failure. 2. Renal failure. 3. If the poison is not excreted by kidney. 4. Electrolyte imbalance. (2) Extra Corporeal Removal of Toxins: Indication: Three of the following: 1. Severe clinical intoxication- for example, Grade 4 coma, hypotension, hypothermia, and hypoventilation in those who have ingested hypnotic drugs. 2. Progressive clinical deterioration despite of the best supportive management. 3. Prolonged coma with complications 4. High plasma concentrations of the toxic agents. 1-Dialysis (a) Hemodialysis: Principle: During hemodialysis, toxin is removed from the blood into a dialysate solution across a semipermeable membrane according to concentration gradient. Indications:  Methanol, salicylates.  Renal failure (corrects pH and electrolyte imbalances).  Liver failure.  Prolonged coma. Criteria for potential dialyzability include: 1. Water solubility. 2. Low molecular weight. 3. Low protein binding. 4. Small volume of distribution. 5. Slow rate of intrinsic elimination (a long t ½). Complications:  Intravenous access complications.  Thrombocytopenia (about 30% reductions).  Leucopenia (about 10% reductions).  Loss of clotting factors.  Lowered urea, creatinine, urate, calcium, glucose.  Hemorrhage because of heparinization.  Patient may disconnect shunt lines.  Air embolism. 8   Infection. 2-Hemoperfusion Principle Is defined as direct contact of blood with a sorbent system. In hemoperfusion, blood is pumped through a column of adsorbent material (charcoal or resin) and returned to the patient’s circulation. Indications: For clearing toxic substances that are poorly eliminated by dialysis [Non dialyzable substances] i.e. High molecular weight, High lipid solubility, High protein binding, Low water solubility. Contraindications:  An antidote is available.  The toxic substance is a rapidly acting.  The substance is "irreversibly" acting for example, organophosphorus insecticide.  The drug ingested is relatively non-toxic for example, a benzodiazepine  The drug has a very large volume of distribution e.g. Tricyclic antidepressant.  Cardiogenic shock. 3- Plasmapharesis A volume of blood is removed, and all blood components except the plasma are returned to the circulation. Indications: Useful for removing protein-bound toxins, such as phenytoin, those are not removed by hemodialysis and are inefficiently removed by hemoperfusion. Complications 1) Hypervolemia or hypovolemia 2) Thrombocytopenia Antidotes Definition: substance which are used to combat the effect of toxin. Classification: 1) Local: i. Physico-mechanical Antidotes e.g. activated charcoal. ii. Chemical Antidotes e.g. tannic acid 2) Systemic: i. Physiological or pharmacological antidotes: 9  These produce effects opposite to that of poison e.g.: -Atropine and oxime for Organophosphorus poison. -Naloxone for Morphine. -N-Acetylcysteine for Acetaminophen. ii. Chelating agents: These substances combine with metals forming nontoxic compounds that are easily excreted in urine: 1- BAL 2- EDTA 3- Deferoxamine (Desferal). 4- D-Penicillamine 5- DMSA TOXIDROMES They are the groups of signs and symptoms that consistently result from a particular toxin (group of toxins). I. Anticholinergic Toxidrome II. Cholinergic Toxidrome III. Sympathomimetic Toxidrome (CNS stimulants) IV. Opioid toxidrome (CNS depressant) V. Sympatholytic Toxidrome Anticholinergics Classification:  Atropine &its derivatives: o Atropine, hyoscyamine.  Antihistamines: o Chlorpheniramine. o Dimenhydrinate. o Diphenhydramine.  Antispasmodics: o Hyoscine.  Mydriatics: o Homatropine.  Other drugs with known anticholinergic effects: o Antipsychotic. o TCA. 10  o Antiparkinsonian. Mechanism of action: Competitively antagonize acetylcholine at muscarinic receptors at: a. Peripheral: Antagonize the muscarinic action of acetylcholine at peripheral receptors: Heart, salivary glands, sweat glands, GI tract, GU tract. b. Central: Stimulation of central nervous system followed by depression. Clinical manifestations due to peripheral action:  Dryness of all secretions, inability to swallow.  Blurred vision.  Fever (atropine fever).  Flushing.  Sinus tachycardia.  Decreased bowel sounds, functional ileus.  Urinary retention. Clinical manifestations due to central action: i. Stimulation stage: - Occupational delirium (Purposeless movements as catching flies or rolling cigarettes), hallucinations (visual, auditory), psychosis, agitation. - Ataxia, disorientation, short-term memory loss. - Restlessness and euphoria. ii. Depression stage: - Drowsiness passing to coma. - Central asphyxia (Respiratory Center depression). Investigations: Toxicological screening ECG shows sinus tachycardia. Treatment:  Initial assessment and stabilization are required.  GI decontamination with activated charcoal.  Control seizures & agitation (benzodiazepines).  Fever control (e.g., fluids, antipyretics, active cooling measures).  Ventricular arrhythmias can be treated with lidocaine. 11   Perform bladder catheterization if signs or symptoms of urinary retention exist.  Hypotension is managed using intra-venous saline infusions, calcium chloride  Specific antidote. o Physostigmine: It is parasympathomimetic, indicated when at least one of the following is present: 1. Tachyarrhythmias with subsequent hemodynamic compromise. 2. Intractable seizures. 3. Severe agitation or psychosis (in which the patient is considered a threat to self or others). - Contraindication: Cardiac conduction disturbances: bradycardia (prolonged PR and QRS intervals) on ECG analysis. o Pilocarpine: it acts peripheral only as it does not cross the blood brain barrier. Antidepressants Classification: 1. Tricyclic antidepressants: Imipramine, amitriptyline, Tetracylic: maprotiline. 2. Monoamine oxidase inhibitor. 3. Non-specific: Lithium. 4. New antidepressant: Selective serotonin reuptake inhibitors SSRI I) Tricyclic Antidepressants Therapeutic uses: - Depression, and panic disorders. - Nocturnal enuresis. - Prophylaxis of migraine. Mechanism of action: 1) Neurotransmitter reuptake inhibition of: Norepinephrine, Dopamine and Serotonin. 2) Receptor blockade: Cholinergic receptors, Alpha adrenergic receptors and Histaminic receptors → Anticholinergic effects & Antihistamine. 3) Cardiovascular effects: - Quinidine-like effects on heart (inhibit Na-K channel) {It is the most important toxic 12  effect.} → conduction defects and arrythmias. - Hypotension due to: direct myocardial depression, peripheral vasodilatation and increased capillary permeability. Toxicity with tricyclic antidepressant is life threatening condition because of: 1. Rapid absorption. 2. Highly bounded to plasma protein. 3. Enterohepatic circulation. 4. Narrow therapeutic index. 5. Multiple ingestion with other drugs. 6. Pre-existing heart disease. Clinical picture: 1. Anticholinergic effects: sinus tachycardia, mydriasis, ileus, hyperthermia, dry mouth, and urinary retention. 2. CNS effects: - Altered mental status: drowsiness, delirium, lethargy and coma. - Respiratory depression. - Seizure. 3. Cardiac effect (due to Na/K channel & α-adrenergic receptor blockade effects): - Conduction delay: prolonged PR, QRS, QT intervals and AV block. - Arrhythmias: Sinus tachycardia (most common arrhythmia, due to hypotension & anticholinergic effect), supraventricular tachycardia, ventricular tachycardia (most common lethal ventricular arrhythmia), ventricular fibrillation, Torsade de point, and Asystole. - Peripheral vasodilatation & hypotension. Investigations: - ECG & continuous cardiac monitoring ( QRS > 0.10 sec ). -Toxicological screening. -Arterial blood gases. Treatment: 1. Gastric Lavage is effective many hours after overdose. 2. Multiple dose activated charcoal (MDAC) is indicated due to enterohepatic circulation. 3. No role for hemodialysis 4. Monitoring: As blood levels correlate poorly with cardiovascular or CNS toxicity so, the ECG changes are often used to determine the degree of toxicity (QRS > 0.1sec is associated with increased risk for ventricular dysrhythmias or seizure). 13 5. Specific antidote: Sodium bicarbonate therapy: Aim: for serum alkalization, indicated when QRS > 0.1 sec with or without arrhythmia. 6. Refractory ventricular arrhythmias: - Lidocaine -Magnesium sulfate - Torsade de pointes: Mg SO4 with correction of electrolyte abnormalities----electrical cardioversion. 7. Hypotension: Alpha-agonists (e.g., norepinephrine, phenylephrine) 8. Seizures: Benzodiazepines are the agents of choice. The big Don’ts - No flumazenil if benzodiazepines are co-ingested (induce seizures) - No physostigmine it may cause bradycardia seizures. Antipsychotics Uses: 1. Schizophrenia, bipolar disorder. 2. Nausea/vomiting, hiccups (chlorpromazine). 3. Pre-anesthesia. 4. Alcohol withdrawal. Classification: Phenothiazines: Chlorpromazine, Promazine, Butyrophenones: Haloperidol Thioxanthines: Thiothixene Mechanism of action: 1. Blockade of dopamine (D2) receptors. 2. Block histamine receptors (H1 and H2). 3. Block muscarinic receptors. (atropine like action) 4. Block α-adrenoreceptors. 5. Block sodium and potassium gated ion channels. Clinical picture: 1- CNS manifestations: - CNS depression: Ataxia, Stupor and Coma. - Hypothermia is common in the elderly. Occasionally hyperthermia. 2- Anticholinergic Effects: Sinus tachycardia, blurred vision, dry mouth, decreased intestinal motility and urinary retention. 3- CVS manifestations: 14  a – Hypotension b- Tachycardia: c- Conduction abnormalities and arrhythmias: tachycardia, ventricular fibrillation. ECG may show prolongation of PR and QT interval, widening of QRS complex, AV block and Torsade’s de pointes. 4- Extrapyramidal manifestations: a. Acute dystonia: Spasm of muscles of tongue, face and neck (spastic torticollis). b. Akathesia: Restlessness (inability to sit still). c. Parkinsonism: mask face, rigidity and tremors at rest. d. Tardive dyskinesia (long term use): - Involuntary, repetitive movements of the face, tongue & lips and chorea of extremities. Movements disappear during sleep. - Mechanism: Chronic blockade of dopamine receptors→ ↑dopamine secretion & hypersensitivity of the receptors. e. Neuroleptic malignant syndrome (NMS): -NMS is caused by sudden, marked reduction in dopamine activity. -It is characterized by 4 cardinal features: ▪ Muscle rigidity (lead-pipe rigidity). ▪ Hyperpyrexia (temperature 38 to 42c) ▪ Mental status changes (confusion, delirium, stupor, and coma) ▪ Autonomic instability (tachycardia, hypertension, diaphoresis & incontinence). Investigations: 1. Routine lab investigations +CPK 2. Toxicological screening. 3. ECG & continuous cardiac monitoring. 4. X-ray abdomen: phenothiazine tablets are radio-opaque. Treatment : 1. Supportive care: 2. GIT decontamination: Gastric lavage- activated charcoal. 3. Arrhythmias: Ventricular (VT, VF, Torsade): HCO3 => lidocaine Bradycardia/AV blocks: temporary pacing 4. Hypotension: Normal saline HCO3 α-agonist vasopressors (norepinephrine). 5. Seizures: Benzodiazepine. 6. Extra-pyramidal manifestations: 15  - Acute Dystonia: benztropine (Cogentin), diazepam. - Akathisia: (reduce the dose, anticholinergics, benzodiazepine). - Parkinsonism: (reduce the dose, add antiparkinsonian, anticholinergics). - Tardive dyskinesia (stops the offending drug, shift to another antipsychotic drug, cholinergic agent). 7. Prevent absorption: Gastric lavage and/or activated charcoal if started within 2 hours of ingestion (rapid absorption). Elimination from blood: Forced diuresis, hemodialysis and hemoperfusion are ineffective due to: 1. Large volume of distribution. 2. Tight binding of the drug to plasma proteins. 8. Neuroleptic Malignant Syndrome a. External cooling with ice; benzodiazepine to decrease muscle rigidity; discontinuation of neuroleptic agent b. Bromocriptine (dopamine agonist) c. Dantrolene (prevent release of calcium) II. Sympathomimetic Toxidrome Central Nervous System (CNS) Stimulants A. Stimulant -Amphetamines -Xanthenes: theophylline, caffeine, theobromine -Cocaine. B. Hallucinogenic -3,4-methylenedioxyamphetamine (MDA). -3,4-methylene-dioxymethamphetamine (MDMA or ‘ecstasy’ or ADAM). -Lysergic acid diethylamide (LSD). -Cannabis Amphetamines Therapeutic uses: - Treatment of the sleeping disorder (narcolepsy) - Treatment of attention deficit hyperactivity disorder (ADHD) in children. Mechanism of action: Amphetamines are sympathomimetic. They increase the release, inhibit the reuptake, and slow down metabolism of catecholamines (epinephrine, norepinephrine & dopamine) leading to marked central and peripheral α- and β- 16  adrenergic receptor stimulation, together with CNS stimulation. Stimulate the release of dopamine and serotonin. Clinical picture of acute intoxication: Stage of stimulation:  Central nervous system: 1. Increased alertness. 2. Euphoria. 3. Excitement, hyperactivity, disorientation, confusion and headache. 4. Dyskinesia. 5. Agitation.  Cardiovascular: 1. Hypertension (due to Alpha- and beta-adrenergic stimulation). 2. Increasing doses produce tachycardia and other dysrhythmias, including ventricular tachycardia and fibrillation. 3. Hypertensive crisis or vasospasm may lead to stroke.  Respiratory: Persons who smoke amphetamines can develop respiratory distress secondary to pulmonary hypertension and pulmonary edema.  Gastrointestinal: - Dry mouth. - Nausea and vomiting. - Diarrhea.  Genitourinary: Urinary retention.  Skin: 1. Diaphoresis. 2. Erythematous painful rashes, needle marks. 3. Infected deep ulcerations (eczema).  Ocular: Mydriasis.  General: 1. Hyperthermia (stimulation of HRC, VC, increase muscular activity). 2. Weight loss, Anorexia. Stage of depression: Coma, cardiovascular& respiratory failure Investigations: 1- Routine investigations. 2- Toxicological screening. 3- Creatine phospho-kinase (CPK), urine myoglobin (hyperthermia & rhabdomyolysis). 4- ECG & continuous cardiac monitoring. 5- Chest X-ray. 6- CT of the head. 17 Treatment:  If No life-threatening conditions: Signs or symptoms may be treated with sedation and observation.  Supportive treatment: ABC.  GIT decontamination: - Do not induce emesis since rapid neurologic and hemodynamic deterioration is known to occur. - Gastric lavage (in the absence of seizures). - Activated charcoal. - Whole bowel irrigation: In body stuffers and packers.  Elimination of the poison from blood: - Hemodialysis used only in renal failure.  Life threatening conditions: 1. Cardiovascular &respiratory failure: Cardiovascular and respiratory resuscitation 2. Hyperthermia: Rapid reduction in core temperature 3. Significant cardiac dysrhythmias: may require cardioversion, defibrillation 4. Hypertension: Use initially benzodiazepine sedation (nonspecific sympatholytic). Refractory cases or cases associated with significant end-organ toxicity can be managed with IV phentolamine (α antagonist), nitroprusside, or nitroglycerin. 5. Agitation or persisting seizures: benzodiazepines N.B. ▪ No beta-blocker for treatment of tachycardia or hypertension as it leaves α- receptors unopposed → V.C → severe hypertension. ▪ No chlorpromazine as it may induce hypotension and convulsion. Causes of death: o Central asphyxia. o Circulatory collapse. o Hyperthermia → rhabdomyolysis (myoglobinuric renal failure), coagulopathy, and multiple organ failure. Cocaine Source: Whitish crystalline powder produced from the dried juice extracted fromthe leaves of the coca plant (Erythroxylon coca). Routes of intake: - Sniffing the powder. - Smoking. 18  - Intra-venous injection. Uses:  Local anesthetic (Marcaine).  Antiarrhythmic (Lidocaine). Mechanism of action: - Sympathomimetic and strong CNS stimulant (blocks the reuptake of catecholamine). - Local anesthetic effect (blocks the inward sodium channels) Clinical picture, and treatment: is the same as amphetamine. Cardiac complications of cocaine:  Increased myocardial oxygen demand with limited oxygen supply.  Vasoconstriction of coronary artery and myocardial infarction.  Accelerated atherosclerosis & thrombosis.  Wide QRS, ventricular tachycardia.  Heart block due to inhibition of conduction. N.B.: - Accidental subcutaneous injection of cocaine may cause localized necrotic ulcers “coke burns”. - Toxicological screening: to detect urinary Benzoylecgonine (main metabolite), detected up to 3 days. Treatment of cardiac complications: Standard: oxygen, nitroglycerin, benzodiazepines Possibly thrombolytics/ angioplasty if occluded coronary artery seen on angiography. Arrythmias: correct metabolic abnormalities, bicarb, & lidocaine. Theophylline Therapeutic uses: - Bronchial asthma and chronic obstructive pulmonary diseases (COPD). - Neonatal apnea. Mechanism of action Theophylline (similarly, Caffeine, theobromine,) at both therapeutic and toxic doses causes: o Adenosine antagonism. o Release of endogenous norepinephrine →stimulation of B1 and B2 adrenergic receptors. o Phosphodiesterase inhibition → increase cAMP (messenger system of B-adrenergic stimulation) Toxic serum level: o Mild to moderate toxicity: 20-30mg/L. o Severe toxicity: > 100 mg/L. Clinical manifestations: 19  CVS: -Tachycardia and ventricular arrhythmias. -Increased blood pressure initially then hypotension later, GIT: -Nausea, vomiting, abdominal pain & diarrhea are very common -Hematemesis CNS stimulation: ‫ارﺗﻌﺎش‬ -Headache, agitation, tremors. -Restlessness and anxiety. -Dilated pupils, hypertonia, hyper-reflexia and convulsions. -hyperventilation Metabolic and electrolyte: - Hypokalemia, hypomagnesemia. - Hyperglycemia and metabolic acidosis. Others: Hyperpyrexia, rhabdomyolysis and acute renal failure. Treatment: Plasma theophylline should be monitored 1-2-hourly until the theophylline level plateau. 1- Supportive measures: ABC. 2- GIT decontamination: - Gastric lavage. - Activated charcoal - Multiple dose activated charcoal (MDAC) is indicated in sustained release pill. - Whole-bowel irrigation (WBI) is indicated in sustained-release pills. 3- Enhanced elimination: Charcoal hemoperfusion and hemodialysis are effective as it has small volume of distribution. Hemoperfusion is effective in removing systemic theophylline. Indications: Patients with severe theophylline toxicity (e.g. serum levels > 100 mg/L) who have intractable vomiting, seizures or arrhythmias, although there is no evidence so far that it reduces morbidity or mortality. 4- Treatment of cardiac arrhythmia: verapamil 5- Ranitidine or metoclopromide may be used to control intractable vomiting. 6- Phenobarbitone is effective in controlling agitation and in suppressing seizures. 20 IV. Opioid Toxidrome (CNS depressants) 1- Opioids -They are related to Narcotic Analgesics. -The term narcotic specifically refers to any substance that induces sleep. -Opium contains more than 20 alkaloids such as morphine, papaverine and codeine. -Opium is ingested or smoked & has a characteristic smell while morphine is injected only & has no smell. Classification of Opioids: 1. Natural: Morphine, Codeine, Thebaine & Papaverine. 2. Semi synthetic: Heroin. 3. Synthetic: Fentanyl, Meperidine, Methadone. N.B. Endogenous opioids endorphins, enkephalins Heroin: - Heroin is a semisynthetic derivative of morphine, with analgesic properties superior to morphine and cough-suppressant properties superior to codeine. - Heroin is six times more addictive than morphine; it is not used medically and not manufactured legally. Mechanism of Action: Opioids bind to opiate receptors in the central nervous system (CNS) and peripheral nervous system (PNS) [mu, kappa, sigma and delta receptors] → a mixture of stimulations and depressions but mainly depressions. I. Stimulation of: 1. Vagal center →slow full pulse and slow deep respiration. 2. Vomiting center →vomiting. 3. Pupillo-constrictor center → pinpoint (non-reactive) pupil. II. Depression of: 1. Cough center →anti-tussive effect. 2. Sensory cortex →analgesia. 3. Consciousness →coma. 4. Respiratory center →central asphyxia. 5. Vasomotor center →circulatory collapse. 6. Heat regulating center → hypothermia Therapeutic Uses: a. Relief pain of terminal illness. b. Preoperative and postoperative medications. 21  c. Acute pulmonary edema. d. Anti-Diarrhea. e. Anti-tussive. f. Obstetrical analgesia. Clinical picture of opioid toxicity o Clinical triad of: CNS depression, respiratory depression, and pupillary miosis. o CNS Manifestations: - Drowsiness, up to coma. - The patient feels euphoria (sense of wellbeing and relief of pains) followed by dysphoria (distress, anxiety and fear). - Analgesia o Respiratory effect: - Severe respiratory depression leading to hypoxia and cyanosis. - Bradypnea. - Rate: up to 4-6 breaths per minute. - Rhythm: irregular (chynestoke) due to depression of the sensitivity of respiratory center to the increase of CO2 - Non-cardiogenic pulmonary edema (due to hypoxia). - Bronchospasm (in asthmatic patient due to histamine release). o Cardiovascular: - Hypotension orthostatic hypotension - Pulse: Slow full regular pulse - Ventricular arrhythmias Temperature: hypothermia (due to depression of HRC &BMR). o Eye Signs: - Conjunctival injection. - Pupillary miosis (due to stimulation of 3rd cranial nucleus). o GIT Manifestation: - Initial nausea & vomiting (stimulation of CTZ), later effect is antiemetic. - Delay gastric emptying, constipation (due to spasmogenic effects on smooth muscles and sphincters). o Skin manifestation: - Pruritis, flushed skin, and urticaria may arise because of histamine release. - Needle tracks are observed occasionally Causes of Death: 1. Central respiratory failure. 2. Acute pulmonary edema. Differential Diagnosis: 22  1. Organophosphorus insecticides. 2. Barbiturates. 3. Ethyl alcohol. 4. Carbolic acid. Laboratory investigations: o Toxicological screening. o Routine laboratory investigations. o Chest x-ray: pulmonary edema. o Abdominal radiation to show body packer &stuffer. o ECG to diagnose arrythmias. o CT scan in patients not responding to naloxone. Treatment: A) Symptomatic: 1. Endo-tracheal intubation and mechanical ventilation to manage respiratory failure. 2. Fluids and inotropic agents as required managing cardiovascular failure. 3. GI decontamination by gastric lavage (even if the toxicity is caused by injection as morphine is re-excreted in the stomach) using activated charcoal. B) Specific antidote: i. Atropine: It blocks vagal stimulation and ↑heart rate (HR.). ii. Antagonists: a- Naloxone: It will reverse the respiratory depression, sedation, analgesia, miosis and nausea (Within 1-2min of administration). It is used in treatment of coma of unknown etiology. However, it does not reverse seizures. - Side effects. It produces an acute withdrawal of opiates and may precipitate shock, seizures, and arrhythmias. b- Nalmefene (Revex): It is a newer opioid antagonist with long duration of action c- Naltrexone: (oral) can't be used for person with acute toxicity, but only in treatment of opiates addiction. Causes of Failure of response: 1. Anoxic brain damage 2. Associated hypoglycemia 3. Concomitant ingestion with another CNS depressant 4. Non-opioid ingestion 2- Tramadol Hydrochloride Tramadol is a centrally acting synthetic analgesic with opioid-like effects. 23 Therapeutic Uses: Analgesic for moderate to severe pain. Mechanism of action: Tramadol is a centrally acting synthetic analgesic with opioid-like effects. It is not derived from natural sources, nor is it chemically related to opiates. Clinical presentation: - Manifestations of over dosage with tramadol are similar to those of opioids. - Convulsions & serotonin syndrome may occur due to its serotonergic effect. Treatment: 1. Supportive measures: ABCs. 2. GIT Decontamination: - Gastric lavage. - Local antidotes: Activated charcoal. 3. Physiological Antidote: Naloxone will reverse respiratory depression, but not all symptoms caused by over dosage with tramadol. 4. Symptomatic: Convulsions: Diazepam. 5. Elimination of the poison from blood: Hemodialysis is ineffective due to high volume of distribution (their plasma protein binding is small) IV. Sedative-Hypnotic toxidromes (CNS depressant) (Minor tranquilizers, Anxiolytics) Uses 1. Treatment of insomnia or anxiety. 2. Anesthetics (thiopental, midazolam). 3. Anticonvulsants (phenobarbital, clonazepam). 4. Muscle relaxants (diazepam). 5. Alcohol withdrawal Members Barbiturates, Benzodiazepines, Miscellaneous Classification Barbiturates Benzodiazepines Ultra short Thiopental (Pentothal), Interval --------------- Short Secobarbital (Seconal) Flurazepam Intermediate Amobarbital (Amytal) Lorzepam (Ativan), Flunitrazepam (Rohypnol) Long-acting Phenobarbital (Luminal) Diazepam (Valium) ‫وﻻ ﻳﺎ ﺑﺮﺑﻴﺘﺎل ﻓﻴﻦ‬ ‫اﻣﻮ ﺳﻴﻜﻮ‬ ‫ﺿﻴﺎ ﻓﻼﻧﺘﺮا ﻣﻊ ﻟﻮر‬ ‫و ﺟﻴﺒﻠﻬﺎ ﻓﻠﻮر‬ Mechanism of action: They enhance the binding of γ-aminobutyric acid (GABA) to GABA receptors. GABA receptors inhibit post-synaptic nerve impulse transmission by causing chloride 24  ion channels to open more frequently, or to stay open for a longer period (thereby increase in the inhibitory synaptic transmission, leading to inhibition of neural activity and CNS depression). Clinical picture of acute toxicity 1. Slurred speech. 2. Ataxia. 3. Incoordination. 4. Coma with depressed reflexes. 5. Respiratory depression. which results in hypoventilation & apnea. - Pneumonia due to:  Prolonged coma.  Inhibition of the protective reflexes (cough reflex).  Aspiration pneumonia following vomiting of gastric contents. 6. Cardiovascular collapse (hypotension due to vasodilatation – depression of vasomotor center- direct myocardial depression) 7. Pupils are usually un-affected, but miosis or mydriasis may occur. 8. Renal manifestations: renal failure due to: - Hypotension → decreased perfusion. - Rhabdomyolysis (due to prolonged coma). 9. Skin manifestations: Blisters “bullae” over pressure points (hands & feet). 10. GIT manifestations: Diminished bowel sounds. Distinguishing Features: 1. Barbiturates: hypothermia and bullae formation 2. Benzodiazepines: tend not to produce respiratory depression during overdose unless taken with other CNS depressants (ethanol). Exceptions are midazolam and triazolam. Complications: 1. Non-cardiogenic pulmonary edema. 2. Hypothermia. 3. Delayed gastric emptying therefore, late lavage and multiple charcoal is effective. Causes of death: Early: central asphyxia or cardiovascular collapse. Late: pneumonias or renal failure. Investigations: 1- Routine investigations. 2- Toxicological screen. 3- Chest X-ray: pneumonia and non-cardiogenic pulmonary edema. Treatment: Supportive care 25 1. Ensure good oxygenation via supplemental oxygen, intubation and/or mechanical ventilation. 2. Prevent absorption: Lavage and/or activated charcoal for ingestion within 2 hours when patients can tolerate the procedure. 3. Elimination of the poison from blood: Forced alkaline diuresis: for long acting barbiturates only (less bound to plasma proteins than short acting and mainly excreted in the urine). Hemodialysis and hemoperfusion (most effective for long-acting barbiturates) and considered in patients with refractory hypotension and severe prolonged coma. Charcoal hemoperfusion is more effective than hemodialysis. 4. Symptomatic treatment N.B. In benzodiazepines, Multiple dose activated charcoal is not indicated. Forced diuresis and hemodialysis are ineffective (high protein binding & large volume of distribution). 5. Provide antidote: -Flumazenil: It is a specific benzodiazepine antagonist. Mechanism: Competitively occupies GABA receptors without causing a functional change in Cl channel. Onset: Immediate. Contra-indications: 1. Chronic use of benzodiazepines, it may induce withdrawal symptoms. 2. Concomitant use of an agent that produces seizures (TCAs). 3. Prior history of non-febrile seizures. 4. Concurrent treatment of seizures. 5. Head trauma (seizures may occur). 26 Over the counter Analgesic Antipyretics Aspirin (Acetyl Salicylic Acid) Pharmakcokinetics&Toxicokinetics: o Absorption: Acetyl salicylic acid is a weak acid; it remains non-ionized in the stomach. Once dissolved, it is absorbed by passive diffusion usually complete in 1 hour. Large single doses of salicylates may delay gastric emptying resulting in continuing absorption for up to 24 hours after the ingestion o Metabolism: Takes place in the liver by conjugation. o Excretion: in the urine. Pharmacological effects: Analgesic, Antipyretic, Anti-inflammatory effects primarily through inhibition of prostaglandin synthesis. Toxic dose: o Mild toxicity 150mg/kg. o Moderate toxicity 150- 300mg/kg. o Severe toxicity 300- 500mg/kg. Mechanism of action: 1. In adults, aspirin toxicity initially causes a respiratory alkalosis because of its direct stimulatory effects on respiratory center. (not observed in children). 2. The second phase of aspirin toxicity results in an anion gap metabolic acidosis. This occurs because salicylate interrupts aerobic respiration by uncoupling oxidative phosphorylation and interfering with Krebs cycle. This results in the anaerobic production of lactate. 3. The interference with aerobic respiration also causes hypoglycemia, fever, fluid loss. Clinical Manifestations of Acute toxicity: o Gastro-intestinal Effects: Nausea, vomiting. o Respiratory System Effects: 1. Increase in both rate (tachypnea) and depth (hyperpnea) of respiration. 2. Non-cardiogenic pulmonary edema, o Cardiovascular Effects: bounding pulse due to peripheral vasodilatation, and hypotension. Tachycardia with pounding bounding o Central Nervous System Effects: 1. Tinnitus and hearing loss due to affection of 8th cranial nerve. 2. Hyperthermia: {due to uncoupling of oxidative phosphorylation & increase of 27  cellular metabolic activity}is an indication of severe toxicity (it is a preterminal condition). 3. Others: include lethargy, which can progress to disorientation, vertigo, seizures, cerebral edema, coma eventually, death. N.B. Salicylism: - Tinnitus, vertigo, deafness may occur with therapeutic and toxic doses. -This effect is due to 8th cranial nerve involvement. It is reversible. o Acid-Base Status: 1. Hyperventilation and respiratory alkalosis (occur initially) due to stimulation of the respiratory center. 2. Ketosis and a wide anion-gap metabolic acidosis due to:  Interference with the Krebs cycle lead to ↑production of ketoacids  Limitation of ATP production, and increase lactate production  Renal compensation by excretion of HCO3.  Impaired renal function due to direct effect leads to retention of phosphoric and sulfuric acid.  Stimulation of lipid metabolism → accumulation of ketone bodies.  Inhibition of amino acid metabolism → accumulation of amino acids. o Glucose Metabolism: Clinical hypoglycemia; due to increased cellular metabolic activity as a result of uncoupling oxidative phosphorylation, in addition to stimulation of insulin secretion (Common in children, rare in adult). o Fluid and Electrolyte Effects: 1. Dehydration because of increased gastrointestinal tract losses (vomiting), diaphoresis and insensible fluid losses (hyperpnea, and from the kidney). 2. Hypokalemia (due to movement of potassium into cells in exchange for hydrogen ions to compensate for the alkalemia) 3. Hypocalcemia o Hepatic Effect (common in children): 1. Hepatitis. 2. Reye syndrome is characterized by nausea, vomiting, hypoglycemia, elevated levels of liver enzymes, fatty infiltration of liver, and coma. o Hematologic Effects: 1. Hypoprothrombinemia and platelet dysfunction are the most common hematologic effects. 2. Bleeding also may be promoted by inhibition of vitamin K–dependent enzymes. o Hypersensitivity reaction (allergy): 1. Urticaria, skin rash and angioneurotic edema. 2. Precipitation of bronchial asthma. Lab Studies: 28  1. Arterial blood gas (ABG): 2. Salicylate concentration: Toxicity of salicylates correlates poorly with serum levels. Range Salicylate concentrations in plasma Therapeutic range 15-30 mg/dL Mild toxicity 30-50 mg/dL moderate toxicity 50-75 mg/dL Serious or life-threatening toxicity >100mg/dL 3. Other lab studies: a) Serum electrolyte. b) Renal & liver function tests. c) Serum glucose levels. d) ABG e) Abdominal X ray: radiopaque concretion of enteric coated aspirin. f) Coagulation studies (prothrombin time and activated partial thromboplastin time) international normalized ratio (INR). Treatment: 1. Limiting absorption, by using activated charcoal, especially if the patient presents within 1 hour of ingestion, MDAC, gastric lavage in all symptomatic patients regardless of time of ingestion. Enhancing elimination, by urinary alkalization & hemodialysis a.Urinary alkalization (most important) Indications: Salicylate concentrations >50 mg/dL accompanied by symptoms and biochemical abnormalities (it should be continued until serum salicylate levels decrease to < 30mg/dL). Benefits: -Prevents reabsorption of salicylic acid from the urine & increases renal clearance of salicylate 10-20 times. -Keeps salicylates away from brain tissue and in the blood due to concomitant alkalization of blood and urine. b. Hemodialysis: Indications:  Severe fluid or electrolyte disturbances.  Renal impairment.  Serum concentrations > 80 mg/dl in adults.  Severe CNS effects.  Acidosis resistant to correction. 2. Correcting metabolic abnormalities and providing supportive care.  Hypokalemia must be corrected. 3. No specific antidote is available for salicylates, and symptomatic treatment can include: 29  a. Demulcents for GIT irritation. b. IV fluids for dehydration. c. Diazepam for seizures. d. Vit. K for bleeding tendencies. e. Cold foments for hyperthermia Acetaminophen(Paracetamol) Analgesic, Antipyretic with no anti-inflammatory effect. Pharmacokinetics &Toxicokinetics: o Absorption: It occurs within 0.5-1 hour, and the peak plasma concentration is reached after 1 hour. o Metabolism: in the liver. Metabolism & mechanism of toxicity: o Normally, 5% of paracetamol is excreted unchanged in the urine. o Approximately 85% of the therapeutic dose is conjugated in the liver (55% with glucuronic acid and 30% with sulphate) to form inactive metabolites which are excreted in the urine. o Smaller amounts (5 - 8%) are oxidized by the cytochrome P450 mixed-function oxidase system to a toxic metabolite (N-acetyl-p- benzoquinoneimine) that is normally conjugated with hepatic glutathione to a nontoxic compound and excreted in the urine. o With glutathione depletion (as in overdose) the N-acetyl-p-benzoquinoneimine is free to bind to macromolecules in the liver cells and cause hepatic necrosis. o NAPQI also causes renal damage (acute tubular necrosis) Fatal dose: 150 mg/kg in a child, & about 7.5 g in adults. Clinical Picture: Stage 1 ( 1day): Anorexia, nausea, vomiting, malaise, fatigue. Stage 2 (1-3days): Apparent recovery, abdominal pain and tenderness, subclinical rise of liver transaminases. Stage 3 (3-4days): Liver failure: o Pain in the right hypochondrium. o Enlarged liver. o Jaundice. o Bleeding tendency. o Increased prothrombin time. o Increased AST, ALT. Stage 4 (4-18days) either: 30  o Recovery: Resolution of liver dysfunction and healing of liver damage occurs within 3-6 months. o Or Death: in severe cases from cerebral edema and sepsis. Prognosis: Only 5% who develop severe hepatic necrosis, progress to hepatic failure, encephalopathy, gastrointestinal hemorrhage, and death. The remainder recovers after 1 - 2 weeks. Complications: (occur in association with hepatic failure): a. Acute renal failure. b. Acute cardiac failure. c. Pancreatitis. d. Non-cardiogenic pulmonary edema. Lab Studies: a. Paracetamol level. b. Liver functions and kidney functions. Management: Firstly, and most importantly: o Airway. o Breathing. o Circulation. The majorities of paracetamol overdose patients present early and are therefore conscious and breathing normally.  If the patient is unconscious the airway must be protected, and tracheal intubation may be required.  In all patients if a significant ingestion(>150mg/kg) or suspicion of significant ingestion has occurred, the following guidelines are used: 1. Within 1-4 hour of ingestion 50 gm of activated charcoal and wait until 4 hours & obtains plasma paracetamol levels. 2. ≥ 4 hours post ingestion obtains plasma paracetamol levels. 3. If below the treatment line, then no further action is required ( 8-24 hr after paracetamol taken, N-acetylcysteine is started and continued or stopped once the blood levels are known. If the quantity is unknown, N-acetylcysteine is started. Specific antidote: N-acetylcysteine  It is a precursor of glutathione, which increases glutathione levels in the liver, therefore, increasing the rate of conjugation of the toxic intermediates.  It also increases the capacity for sulfation of acetaminophen 31   Most effective if started within 8-10 hrs after ingestion  Can be given PO (Mucomyst) or IV ( Parvolex) Oral dose: loading 140 mg/kg then 70 mg/kg /4hours for 3 days.  Side-effects of IV treatment: Flushing, hypotension, wheezing, anaphylactic reaction. N.B. The alternative is methionine Indication of administration: If the blood paracetamol level Duration At Paracetamol level 4 hr ≥ 200 mg/L 8 hr ≥ 100 mg/L 12 hr ≥ 50 mg/L 15hr ≥ 30 mg/L Iron Toxicity Uses: Iron is used as a paediatric or prenatal vitamin supplement and for treatment of anaemia. Pharmacokinetics &Toxicokinetics: o Absorption: It absorbed into the GIT o Distribution: It remains in the blood or transported to the liver or spleen and stored as ferritin or hemosiderin. o Excretion: In the stools. Mechanism of Toxicity: Local: - Corrosive damages to gastrointestinal (GI) mucosa → Vomiting & bloody diarrhea. - Acute gastroenteritis may contribute to early cardiovascular toxicity through fluid and blood loss. Systemic: Cardiovascular system: iron causes massive post-arteriolar dilation leading to venous pooling, this followed by increased capillary permeability leading to hypotension and shock. - Iron has direct myocardial depressant effects. Liver: Free iron accumulates in Kuppfer cells then hepatocytes leading to periportal necrosis. Metabolism: iron produces metabolic acidosis due to: - Conversion of ferrous iron to ferric iron with release of hydrogen ions. - Disruption of the oxidative phosphorylation, leads to anaerobic metabolism - Hypovolemia and hypoperfusion 32  Nontoxic ingestion: < 20 mg/kg (< 1.5g/70kg) of elemental iron. Mild to moderate toxicity: 20-60 mg/kg of elemental iron. Potentially serious or life-threatening toxicity: > 60 mg/kg of elemental iron. Clinical presentations: Phase 1: Occurs within 6 hours post ingestion. GIT manifestation: Vomiting, hematemesis, diarrhea, abdominal pain. CNS: restlessness, lethargy, convulsions and coma (if the circulatory blood volume is sufficiently compromised). In Severely intoxicated patients: early onset of shock and metabolic acidosis occur. Phase 2: (6- 24 hours): This is a stage of apparent improvement which may be misleading and transient. This stage may not be seen in severe poisoning. It is due to redistribution of free iron from blood Phase 3: Begins after 24 - 48 hours. a. Worsen of GI hemorrhage. b. Hypovolemic shock and cardiovascular collapse. c. Lethargy, coma. d. Severe metabolic acidosis. e. Coagulopathy. f. Fever. g. Pulmonary edema &renal failure. Phase 4: Occurs 2-4 days post ingestion. It is Characterized by major organ system failure; predominantly hepatic necrosis, renal failure, metabolic acidosis, bleeding diathesis, pulmonary edema, coma and death in severe cases. Phase 5: Occurs 2-6 weeks post ingestion and is characterized by late scarring of the GI tract causing pyloric obstruction or hepatic cirrhosis. Laboratory investigations: Serum iron level: Blood should be taken 4 hours post-ingestion due to delayed absorption. - Mild toxicity: 300 µg/dL - Serious toxicity: 500 µg/dL Glucose levels exceeding 150 mg/dL are common with severe iron toxicity. Abdominal x-ray: (Radiopaque iron tablets could be detected). Do not delay treatment for radiography. Treatment: General measures: o Emesis is often recommended within 2 hours after ingestion, if the patient has had no spontaneous vomiting. o Gastric lavage with a large bore orogastric tube may be unsuccessful because iron 33  tablets are relatively large and become sticky in gastric fluid. o Whole bowel irrigation used to speed the passage of undissolved iron tablets through the GI tract. A polyethylene glycol electrolyte solution is used. o Treat metabolic acidosis by NaHCO3. o Fluid and electrolyte balance. o Deferoxamine oral to bind Iron in GIT. Chelation therapy: Deferoxamine may be administered either IM or IV. The IV route is administered as a continuous infusion. Indications: - Indicated in all cases with signs of systemic intoxication (shock, metabolic acidosis, coma), - Serum iron greater than 500 µg/dL or estimated ingested dose greater than 60 mg/kg elemental iron. - Initiate chelation when a serum iron level is not available, and symptoms are present. Endpoints o Return of urine color from vin-rose to amber. o Dissipation of symptoms (acidosis, shock). o Serum iron of ≤100µg/dl. Prescription Drugs Cardiovascular Drugs Beta-adrenergic blockers Therapeutic Uses: a. Hypertension. b. Post myocardial infarction. c. Migraine headaches. d. Essential tremors. e. Thyrotoxicosis. f. Glaucoma. g. Anxiety Mechanism of Action: They induce blockage of beta-receptors resulting in decreased production of intracellular cyclic adenosine monophosphate (cAMP) with a resultant prevention of multiple metabolic and cardiovascular effects of circulating catecholamine. Beta 1-receptors blockers: Reduce heart rate, blood pressure, myocardial contractility, and myocardial oxygen consumption. 34  Beta 2-receptor blockers: 1. Inhibits relaxation of smooth muscle in blood vessels, bronchi, and the gastrointestinal and genitourinary tract. 2. Inhibits glycogenolysis and gluconeogenesis. Classification: Non-selective B blocker e.g. propranolol (Inderal) is the most dangerous Selective: Atenolol (Tenormin) Clinical Picture: o Individual response to B-blockers overdose is variable. o Manifestations appear within 4 h of ingestion, can be delayed for 6-12 hours for sustained released formulation: Cardiovascular Manifestations 1. Hypotension & Bradycardia are common manifestations. 2. Prolonged PR interval, first degree heart block, AV block & BBB. 3. In severe toxicity: asystole, cardiac arrest, ventricular arrhythmia & cardiogenic shock in patients with pre-existing heart disease. Respiratory Manifestations: 1. Pulmonary edema may occur in patients with pre-existing heart disease. 2. Respiratory depression. 3. Bronchospasm in susceptible individuals. CNS Manifestations: Drowsiness, dilated pupils, hallucinations, seizures and coma. Others: Hypoglycemia, Hyperkalemia. Lab investigations: 1. Frequent blood sugar in diabetics and children is recommended. 2. Blood levels of B-blockers don't correlate with toxicity & have no value in management. 3. ECG &continuous cardiac monitoring. Treatment: 1- ABCs measures: Pre-administration of atropine before intubation to blunt vagally mediated bradycardia associated with laryngoscope. 2- GIT Decontamination: Gastric lavage and oral charcoal within 1hr post ingestion in non-sustained release formulations. Whole bowel irrigation & repeated oral charcoal in sustained release preparations. 35  3- Enhanced elimination: It is ineffective for high lipid- soluble beta antagonist, but it is effective for low lipid- soluble beta antagonist. 4- Management of hypotension and bradycardia: o IV fluid & atropine o Glucagon (specific antidote): (Drug of choice in hemodynamically compromised patients i.e. BP< 80 & HR < 40). o Catecholamines. o Insulin and Glucose: Positive inotropic effects. Insulin causes direct myocyte activation which increases inotropy. Essentially, myocytes in a stress state rely on carbohydrate metabolism and insulin promotes glucose uptake and utilization. o Cardiac pacing if no response to drug therapy. Differential Diagnosis: 1. Ca-channel-blocker overdose. 2. Digitalis overdose. 3. Clonidine overdose. 4. Acute myocardial infarction with cardiogenic shock. Calcium Channel Blocker Prescribed for: Angina -Myocardial infarction – Hypertension -Migraine – Supra-ventricular tachycardia. Mechanism of Action They diminish the entrance of calcium into cardiac and smooth muscle of blood vessels, producing the following 4 cardiovascular effects: 1. Peripheral vasodilatation 2. Negative chronotropic effect (decreased heart rate) 3. Negative inotropic effect (decreased cardiac contractility) 4. decreased cardiac conduction (decrease SA node & AV node) Types: 1. Verapamil (e.g. Isoptin). 2. Nifedipine (e.g. Procardia, Adalat). 3. Diltiazem (Cardizem). 4. Amlodipine. Clinical Picture of acute toxicity: ( within 2-4 hrs)  Hypotension is the most common physical finding (due to: peripheral vasodilatation, bradycardia and negative inotropic effect). 36   Bradycardia, with variable degrees of heart block.  Altered mental status (due to hypotension & hypoperfusion) or seizures.  Hyperglycemia (is a common finding) & suppression of insulin release from the pancreas  Hypokalemia or hyperkalemia  Lactic acidosis Treatment: 1- ABCs measures 2- GIT Decontamination: 1. Gastric lavage and oral charcoal within 1hr post ingestion in non-sustained release formulations. 2. Whole bowel irrigation & repeated oral charcoal in sustained release preparations. 3- Hypotension and bradycardia : 1. Calcium (10% solution) 2. Glucagon: (Increases cyclic AMP) may be used in patients with hypotension who do not respond to Ca salts. 3. Atropine for bradycardia with hemodynamic compromise. 4. Insulin and Glucose: - Positive inotropic effects. 5. Dopamine 6. Epinephrine 7. Cardiac pacing may also be required in unresponsive cases. 4- Enhanced elimination: Diuresis, dialysis, and hemoperfusion are largely ineffective due to: - Large volume of distribution. - Tight binding of the drug to plasma proteins. Digitalis Uses: - Chronic heart failure. - Atrial fibrillation. Mechanism of Action: 1) Therapeutic dose: - Stimulation of the Vagus nerve which → –ve chronotropic (↓H.R.) i.e. Elongation of the diastolic phase and improved filling of the heart due to bradycardia. - It inhibits Na–Ka ATPase in the cardiac muscle fibers → increased intracellular Na and Ca and increased extracellular K →improved cardiac contractility (+ve 37  Inotropic). 2) Toxic dose: Inhibition of Na–Ka ATPase together with the electrolyte imbalance especially hyperkalemia → arrhythmias and worsening of heart failure. Clinical Picture: Toxicity may be acute or chronic (due to cumulative effect) Constitutional symptoms: (e.g., weakness, fatigue). Visual manifestation: - Halos or rings of light around objects (tendency to yellow-green coloring). - Blind spots in vision. - Blurred vision. GIT: Anorexia, nausea, vomiting{ due to a direct action of digitalis on chemoreceptor trigger zone (CTZ)}, and diarrhea, are early features of Toxicity Central nervous system: Confusion, headache, drowsiness, agitation, delirium, and hallucinations. Cardiovascular: 1. Dysrhythmias : - Premature ventricular contractions (PVC’s) {ventricular bigeminy or trigeminy). - Acute Toxicity: bradyarrhythmias (due to vagal stimulation). - Chronic Toxicity: - Ventricular tachyarhythmias are more common in chronic or late acute poisoning. - Bradyarhythmias (due to direct actions on the heart and so minimally responsive to atropine). 2. Hypotension. Electrolytes: - Hyperkalemia: in acute toxicity (Renal insufficiency is a risk factor) it may also occur with chronic toxicity. - Hypokalemia: in chronic toxicity (due to use of loop diuretics, diarrhea and poor dietary intake). Investigations: 1. Routine laboratory investigation: - Hyperkalemia in acute toxicity and it is a primary predictor of need for antidotal therapy. 38  - Hypokalemia in chronic toxicity. - Kidney function tests (renal impairment alters elimination of glycosides). - Serum calcium levels should be monitored during therapy, as hypercalcemia from any cause will predispose patients to digoxin toxicity and serious arrhythmias. 2. Toxicological screening (Digoxin level): - Therapeutic blood level is 1- 2 ng/ml. - Toxic blood level is 2.5 - 4 ng/ml. - Concentrations exceeding 12 ng/ml carry serious prognosis. 3. ECG and continuous cardiac monitor. Treatment: 1. Prevention of further exposure. 2. Basic management (ABC). 3. Activated charcoal. 4. Electrolyte disturbances: -Hyperkalemia: a. Sodium bicarbonate and/or glucose - insulin are indicated. b. Digoxin-fab fragments. c. Hemodialysis. d. NEVER give Calcium. -Hypokalemia: give Kcl 5. Bradycardia:  Hemodynamically stable: May be treated with observation and discontinuation of the drug.  Hemodynamically unstable bradycardia: - Respond best to Digibind. - Atropine may be used - Cardiac pacing. 6. Tachycardia: - Lidocaine. - Magnesium sulphate 7. Digoxin specific antibody (Digibind) Each vial of the drug contains 40 mg of Digoxin-specific antibody fragments. Indications: 1-Serum digoxin level above 10ng/ml in adults and >5 ng/ml in children. Or ingested dose ˃ 10 mg in adults. 2- Severe cardiac arrhythmias. 3- Severe hyperkalemia (> 5.5 mEq/L). 4- Heart block. 39  Unknown acute ingestion or unknown drug level: Rapidly administer 10 vials, repeat dose with 10 vials is indicated if there is no or only partial clinical response. 8. Elimination of the poison from blood: - Forced diuresis, hemoperfusion, and hemodialysis are ineffective because of its large volume of distribution (their plasma protein binding is small). - Plasmapheresis may have a role for removing retained Fab-digoxin complexes to prevent rebound toxicity. Household intoxication Caustics & Corrosives These are chemicals having strong local destructive properties. Classification: Class Inorganic corrosives Organic corrosives Effect Strong Mild Action Local only Local and remote Examples - Acids: as sulphuric acid, - Carbolic acid (phenol) Hydrofluoric acid and - Oxalic acid Nitric acid. - Alkalis: As NH4OH, NaOH and KOH (Potash) Inorganic corrosives Mechanism of action: Acids Alkali Action Coagulative necrosis → Eschars Liquefactive necrosis→ formation→ Limits penetration. Saponification → continue to penetrate. Main affected site Stomach. Oropharynx, Esophagus Complications Perforation can occur when eschar -Stricture formation sloughs. -Fistula -Cancer esophagus Clinical picture: Ingestion:  Immediate severe burning pain in mouth, chest and abdomen.  Dysphagia, thirst& increased salivation.  Vomiting may be bloody.  Erythema, edema and ulceration of mouth.  Stains and burns around the mouth.  Esophageal and pharyngeal edema may occur. 40   Shock, hypotension, tachycardia and altered mental state. Metabolic acidosis. Dermal: Full-thickness skin loss, and they destroy ectodermal elements in hair follicles and sweat glands. Ocular: Pain, lacrimation, conjunctivitis, corneal ulceration. Inhalation: Cough, Hemoptysis, Dyspnea & stridor, Acute pulmonary edema. Acute complications -Acute upper airways obstruction (laryngeal edema). -GIT hemorrhage. -Signs of perforation: esophageal (leads to mediastinitis, pericarditis, pleuritis) or gastric (acute abdomen) -Sepsis. -Fistula formation. Chronic complications: Esophageal obstruction, Pyloric stenosis, Cachexia, Carcinoma of the esophagus. Investigations: 1) Laboratory Tests: Routine lab investigation. 2) Radiology: Chest X-ray: Abdominal X-ray 3) Endoscopy: Should be done within 12 hours. Contraindicated in airway obstruction and in cases of perforation. Treatment: a. Asymptomatic patient: only observation in the Emergency Room. b. Symptomatic patient: 1- Supportive care: ABC Strong analgesic for pain: 10mg morphine IV. 2- GIT Decontamination: It is CONTRAINDICATED to do the following: Induced emesis: Causes reintroduction of the caustic to the upper gastrointestinal tract and airway. Activated charcoal: - It interferes with tissue evaluation by endoscopy. - Most caustics are not adsorbed to activated charcoal. Gastric lavage: carries the risk of perforation. Neutralization and dilution: 3- Decontamination of the skin and eyes: 4- Local antidote: Milk to attenuate the heat generated by a caustic. 5- Symptomatic: 41  - Corticosteroids - Antibiotics - Nutrition 6- Surgical procedures: - Tracheotomy - Gastrostomy, gastrectomy or esophagectomy with colon interposition. Organic acid corrosives Carbolic acid (phenol) It is a coal tar derivative, with characteristic smell. Present in: Dettol, Lysol, phenol detergent (Disinfectant). Action: local & systemic effects. Local:  Weak corrosives: leading to superficial ulcers.  Coagulative necrosis: leading to thickening of gastric mucosa.  Local anesthetic action: leading to transient pain & vomiting. Systemic: 1) CNS: Phenols stimulate and then depress the CNS. Brief stimulation may be related to increased acetylcholine release, but prominent effects are CNS depression. 2) CVS: Phenols have direct myocardial depressant effect. 3) Respiration: Phenols stimulate respiratory centers and produce a respiratory alkalosis. Metabolic acidosis follows because uncompensated renal loss of base during stage of alkalosis due to renal damage. 4) Methemoglobinemia: Phenol and certain phenol derivatives (hydroquinone and coal tar) cause methemoglobinemia. 5) Kidney: Acute glomerulonephritis. Clinical presentation: A- Local: Stomach: Pain + Vomiting with characteristic smell [temporary due to local anesthetic effect]. Skin: Whitish eschars around the mouth or skin which turns brown on exposure to air. B- Systemic effect: 1) CNS: Constricted pupil and convulsions rapidly followed by coma & respiratory failure. 2) CVS: Cardiovascular collapse, shock and arrhythmias. 3) Kidney: Acute glomerulonephritis: Oliguria with albumin blood & casts. Anuria [uremia], the urine turns green on exposure to air [Hydroquinone]. Investigations: 1) Renal function tests. 2) Urine analysis: green in color. 42  3) Methemoglobin level. 4) Blood pH and electrolytes. Treatment: 1) Supportive measures: ABCs  Respiratory: Ventilatory support/ oxygen; intubate if necessary.  Cardiovascular support: a) Keep patient warm and recumbent. b) Use IV saline and pressors to support the blood pressure. c) Use lidocaine for ventricular arrhythmias.  Diazepam for seizures, if no response, phenytoin or phenobarbitone may be given. 2) GIT Decontamination:  Emesis is not recommended due to: - Rapid onset of coma and seizures (within half an hour for significant ingestion). - Corrosive action of phenol.  Gastric lavage is indicated and essential  Local antidote is: - Milk & egg white: as phenol will coagulate their protein instead of stomach protein. - Ethanol 10% dissolves phenol. 3) Elimination of the absorbed poison: Dialysis [peritoneal & hemodialysis] 4) Symptomatic:  Renal failure [dialysis].  Methemoglobinemia more than 30% [methylene blue 1-2 mg/kg].  Acid-base disorders [dialysis]. Kerosene Clinical picture: - GIT irritation: nausea, vomiting, abdominal colic, diarrhea. - Lungs: aspiration pneumonia (its vapors may enter the respiratory tract). - CNS depression: Due to: Direct effect, hypoxia due to chemical pneumonitis and acidosis. This leads to: drowsiness, cyanosis, coma. Cause of death: - Central respiratory failure. - Bronchopneumonia. Treatment: - Restore vital functions. - Elimination of kerosene: 43  o Never do emesis. o Never do stomach wash; unless a cuffed endotracheal tube is used, and we can use liquid paraffin to form a layer to cover the stomach contents and prevent vaporization. - Antidotes: no specific antidote - Atropine can be used to dry the secretions. - Symptomatic measures: - Chemical pneumonitis: non-steroidal anti-inflammatory drugs - Bacterial pneumonitis: specific antibiotics. Pesticides They are compounds that are designed to kill various pests (plant or animals). They are divided into:  Insecticides: which include: - Organophosphorus compounds. - Carbamate compounds. - Organochlorine insecticide. - Pyrethroids.  Rodenticides : which include: - Warfarin. - Strychnine. - Phosphorous, zinc phosphide. INSECTICIDE (Organophosphorus Compounds) (Cholinergic Toxidrome) They are used as liquid or powder. They are absorbed by ingestion, inhalation or through the skin (inhalation is the most rapid route). Members:  Parathion.  Malathion.  Sarin& soman.(war gases) Mechanism of toxicity: Organophosphates inhibit cholinesterase → accumulation of acetylcholine → stimulation followed by depression of: Nicotinic receptors. Muscarinic receptors. CNS. They act by irreversible binding of their phosphate radicals to the cholinesterase enzyme forming phosphorylated enzymes. Within 48 hours after phosphorylation, the enzyme complex loses an alkyl group in a 44  process called “aging”. Aged enzymes cannot regenerate spontaneously. Clinical picture: Symptoms begin after 30 - 60 min after exposure, reaching a maximum after 2 - 8 hr. In some cases, symptoms may be delayed for up to 12 hr. 1. Muscarinic receptors effects: (DUMBBLES) Diarrhea, Urine incontinence, Miosis, Bronchospasm, Bradycardia, Lacrimation, Emesis and Salivation. ‫في الغالب المريض بيجي بيها‬ 2. Nicotinic receptors effects: - Musculoskeletal: Fasciculation → paralysis. - Cardiovascular (Sympathetic ganglia): tachycardia & hypertension followed by bradycardia & hypotension. 3. CNS effects: - Stage of stimulation: anxiety, irritability, and convulsions. - Stage of depression: coma, and depression of both respiratory & cardio- vascular centers. 4. Other effects: - Metabolic acidosis. - Hyperglycemia. - Non-cardiogenic pulmonary edema. Late sequelae: 1- Intermediate syndrome: - Begins after 3 days and lasts for 30 days. - Characterized by: paralysis of proximal muscles of the limbs, neck flexor muscles, and respiratory muscles. - The condition is not responsive to Atropine or Pralidoximes, but early & adequate treatment of toxicity with Pralidoximes may prevent the syndrome. 2- Delayed peripheral neuropathy: - Begins after 3 weeks. - The neuropathy begins by paresthesia (glove & stocking), and pain in the calves followed by weakness “toe drop” that rapidly progresses to flaccid paresis. - The condition may be ascending as seen in Guillain-Barre syndrome. - Treatment is difficult & no role of antidotes. 3- Fatal pancreatitis: develops with parathion intoxication. N.B. the main cause of death is respiratory failure. Investigations: 1. Routine lab investigation. 2. Cholinesterase levels: - True cholinesterase present mainly in erythrocytes and nervous tissues (good 45  for non-acute exposure monitoring). - Pseudo-cholinesterase found in plasma and liver (quick fall and quick recovery after exposure so it is good for acute exposure monitoring). 3. Detection of para-nitrophenol (metabolite of organophosphate) in urine. 4. Chest X-ray: pneumonia, non-cardiogenic pulmonary edema. 5. ECG: arrhythmia. Treatment: Prophylactic:  Protective clothes, gloves.  Never eat or drink during work.  Do not use empty containers for storing food.  Keep containers away from the reach of children. Curative:  Patient decontamination by H2O & Soap, remove patient's clothes.  Correct the vital functions. Take care of respiration. Keep patent airway.  Elimination: gastric lavage by Na Hco3.  Antidotal measure: A- Atropine sulfate (physiological antidote). - It is competitive antagonist of acetylcholine at muscarinic receptors. It crosses BBB, so it treats both muscarinic and central effects, it will not reverse the neuro muscular paralysis. - End point for the treatment: Clearance of bronchial secretions. Patients must be observed for at least 24hr after the last dose of atropine. B- Oximes (specific antidote): They reverse phosphorylation & regenerate the cholinesterase. They antagonize both muscarinic & nicotinic actions. It must be given in the first 24-48 hours i.e. before enzyme aging (phosphorylation by covalent bond): - Pralidoxime (PAM) - Its beneficial actions are directed towards skeletal muscle activity and because of this; atropine must be given if the patient is to be successfully antidoted. Continue therapy till muscles resolve & atropine is no longer required.  Control seizures by benzodiazepines. Carbamates (Cholinergic Toxidrome)  These compounds are reversible inhibitors (short duration) of cholinesterase enzyme (carbamylation). They are used for household and agriculture insects e.g. carbaryl & methyl carbamate.  They have the same clinical picture as organophosphorus. 46 Difference between carbamates & organophosphates: - They are reversible cholinesterase inhibitors, so they are less toxic & of shorter duration than organophosphates. - Carbamates have rapid onset (15 – 120 minutes). - Carbamates poorly cross the blood brain barrier, so no CNS effects. - Carbamates have no long-term sequelae. - Serum and red cells cholinesterase values are not reliable in the diagnosis of Carbamate poisoning. The enzyme activity with Carbamate poisoning return to normal within few hours. - Oximes are not indicated in the treatment of carbonates since aging of the enzyme does not occur. Treatment: - Atropine sulfate to be repeated until full atropinization. - Care of respiration. - Anti-convulsant. - Oximes are not used due to rapid regeneration of cholinesterase enzymes, and PAM itself is a weak inhibitor of the enzyme. RODENTICIDE Aluminium Phosphide Mechanism of Action: Aluminium Phosphide is changed to phosphine gas (in the presence of moisture and acid in the stomach). Phosphine gas has the following actions: - Cytochrome C oxidase inhibitor (responsible for cellular respiration). - Gastrointestinal and pulmonary irritant. Clinical picture: 1- Gastrointestinal: Nausea & vomiting. 2- Cardiac: sever refractory shock, sever hypotension 3- Respiratory: Pulmonary edema, cough & dyspnea. 4- Hepatic: Centrilobular necrosis. 5- Metabolic: Metabolic acidosis. 6- Central nervous system: Headache, fatigue, ataxia 7- Neuromuscular: Paresthesia & kinetic tremors. 8- Ocular: Diplopia. Investigations: 1- Routine lab investigation. 2- Detection of zinc phosphide. Treatment: 47  1-Supportive treatment: ABC. 2-Decontamination: GIT: - Emesis should be avoided (vomiting), avoid water ingestion as it increase phosphine gas release - Gastric lavage - Activated charcoal. Skin: Skin wash with copious water. Inhalation: 100% humidified oxygen. 3-Symptomatic treatment: - Acidosis: sodium bicarbonate. - Pulmonary edema: Oxygen & mechanical ventilation. Chemical Asphyxiant Carbon Monoxide It is a colorless, odorless, and non-irritant toxic gas 'The Silent Killer’ Sources: - Exogenous sources: It is a product of incomplete combustion of hydrocarbons.  In an urban environment nonsmokers have CO-Hb level 0f 1-2%  Tobacco smoke contain 4% CO and smokers have a level of 4-9% CO-HB - Endogenous sources: Normal hem- catabolism. Conditions of Poisoning: Accidental: 1- Household: Any fuel-burning appliance that is not vented properly, such as: Charcoal grills, Wood burning chimneys or Gas heaters and stoves. 2- Environmental Automobile exhaust gas or Cigarette smoke. 3- Occupational Firemen or Coal miners. Suicidal: Painless death due to inhalation of automobile exhaust in a closed garage. Mechanism of Toxicity 1. CO has greater affinity (250 times) to Hb than O 2 leading to: - Reduction in O2 carrying capacity of the blood → Cellular hypoxia - Decrease O2 dissociation to the tissues → shift O2 dissociation curve to left. 2. CO binds to other iron-containing proteins: - Myoglobin: causing myocardial (reduced cardiac output and hypotension) and 48  skeletal muscle dysfunction. - Cytochrome oxidase, which responsible for allowing cells to utilize oxygen 3. Free radical formation leads to cellular injury and neuronal dysfunction. Clinical Presentation : Depends upon carboxyhemoglobin level: Mild ( 20 - 40% COHb): - Confusion. - Syncope, chest pain (myocardial ischemia) and tachycardia. - Tachypnea & dyspnea. - Weakness, impairment of vision & hearing and ataxia (unable to escape or call for help) - Rhabdomyolysis. Severe (> 40 - 60% COHb): - Palpitations, dysrhythmias, hypotension, myocardial ischemia & cardiac arrest. - Pulmonary edema & respiratory arrest. - Seizures and coma. Fatal (> 60% COHb). Other symptoms: Metabolic acidosis, due to lactate formation from relative hypoxia Severe poisoning will result in rhabdomyolysis, especially in comatose patient Renal failure, this can develop from direct CO toxicity and myoglobinurea. Cherry-red coloration of the skin. Bullae may also result from either pressure necrosis or direct toxic effects of CO on the epidermal-dermal junction. Neurological sequelae (complications): They may occur at the onset of intoxication or days to weeks later after a period of apparent total recovery. The severity of these symptoms depends on the duration of hypoxia of brain tissue and the neurological structures affected. They include: - Amnesia. Parkinsonism & paralysis. Confusion. Disorientation. - Encephalopathy. Mental retardation. Psychosis and manic depression. Lab investigations: - Co-Hb level (co-oximeter): It is the most useful diagnostic test. - Arterial blood gas for metabolic acidosis. 49  - Creatine phosphokinase (CK) for rhabdomyolysis, in comatose patient. - Finger stick glucose test to rule out hypoglycemia in confused patients. - ECG. Causes of death: Respiratory and circulatory failure Treatment: 1-antidote therapy: A-100% O2 for 4hr: Its benefits:  Reduces the half-life of CO-Hb from about 4 -5 hours to 1 hour.  Dissolve O2 in plasma delivering it directly to the tissues  Accelerate rate of O2 dissociation. B-Hyperbaric O2: O2 administration under pressure >1atmosphere. Its benefits:  Increase rate of dissociation of CO from hemoglobin and cytochrome oxidase.  Decrease T½ of CO to 23 min.  Increase dissolved O2, readily available to tissues  Prevent lipid peroxidation which is responsible for neuronal dysfunction. Indications of Hyperbaric O2:(COHb level > 25%) 1. Seizures, coma. 2. Ventricular arrhythmia, MI 3. Any neurological deficit. 4. Persistent neurological symptoms after 100% O2 treatment. Symptomatic treatment: 1. Hypotension which can be treated with fluids and vasopressors as needed. 2. Seizures: routine administration of benzodiazepine. 3. Protect the kidneys with aggressive hydration to increase urination. 4. Monitor the patient for further respiratory distress Substances of Abuse Classification: Narcotics (opioids). Depressants: Alcohol, Chloral Hydrate, , Rohypnol. Stimulants: Cocaine, , Amphetamines, Methamphetamines. Hallucinogenic: LSD, Ecstasy. Cannabis. Inhalants: Anesthetics (nitrous oxide, halothane, ether). Solvents, paints, sprays and fuels. 50  Ethyl Alcohol Ethyl alcohol (Ethanol) is a clear, colorless liquid that has a very slight pleasant odor. Toxicokinetics : o Absorption: o Major (80%) (From small intestine). o Minor (20%) (From stomach & large intestine). - Fatty food delays its absorption. - Gastric emptying accelerated by tolerance. o Distribution: - To all tissues and body fluids (equivalent to the water content of tissues) - Passes the alveolar membrane, the blood brain barrier as well as placenta. o Metabolism: - 90-98% of the absorbed ethanol is removed from the body by enzymatic oxidation primarily in the liver but to a lesser extent in the kidney. - Ethanol (by the effect of Alcohol dehydrogenase) is transformed into Acetaldehyde which (by the effect of aldehyde dehydrogenase) is transformed into Acetic acid (enter Krebs cycle to form. CO2 &H2O). Alcohol dehydrogenase metabolizes ethanol at a constant rate of 7 - 8 g/hr to acetaldehyde and NAD to NADH. o Excretion: - 10% Ethanol excreted unchanged through: - Urine (5%). - Breath (5%). - Small amounts can be detected in sweat, tears, bile, gastric juice and other secretions. Mechanism of action: 1) CNS: Depression is the principal effect of ethanol. Ethyl alcohol depresses the central nervous system in descending order, from cortex to medulla, depending on the ingested amount. Ethanol exerts its action through direct effect on neuronal membrane possibly due to inhibition of Na-K ATPase. The effect of ethanol on the CNS is directly proportional to the blood concentration. The effect of alcohol is potentiated by concomitant ingestion of depressant drugs as barbiturates 2) Peripheral:  Vasodilatation which is the cause of false sensation of heat (Heat regulating center is inhibited, so temperature is low).  Ethanol metabolism: Ethanol leads to significant decrease in NAD/NADH ratio in the liver. This results in: - Significant hypoglycemia partly due to inhibition of gluconeogenesis. - Reduction in the metabolism of glycerol, resulting in accumulation of fat in the 51  liver. - Accumulation of lactic acid & ketoacids [metabolic acidosis] Clinical presentation: Depends on blood Ethanol level 1) Mild toxicity: [stage of excitation] Inhibition of the inhibitory control of cerebral cortex.  Blood alcohol level ranges between 50-150 mg %.  There is inhibition of centers which control judgement & behaviors.  Euphoria, increased attention.  Talkativeness and behavioral changes and sexual crimes.  Increased appetite. 2) Moderate toxicity: [stage of incoordination]:-  Blood alcohol level ranges between 150-300 mg %.  Motor incoordination (Muscle incoordination):-  Drunkard (staggering) gait.  Tremors of hands.  Slurred speech.  Decreased motor skills.  Diaphragm: Sudden contraction leading to Hiccough.  Eyes: Diplopia.  GIT: Vomiting (local gastric irritation and irritation of CTZ. by acetaldehyde).  Skin: Flushed (alcohol flush) & sweating. 3) Severe toxicity: [stage of seizures & coma]  Blood alcohol level is more than 300 mg %.  Severe depression of medullary centers. a) Seizures. b) Shock: - Temp :decreased. - B.P : hypotension. - Pulse : rapid & weak. - Respiration: slow & shallow. c) Breath :Alcoholic smell. d) Pupil : constricted pupil (usually). McEwen’s sign pupils (changeable pupils): contracted but dilate on pinching the skin of face or neck. e) Coma with re