Questions and Answers
Which patients are usually victims of chronic intoxication?
Hemodialysis is effective in rapidly removing salicylate.
True
What are the typical signs and symptoms of acute intoxication?
Nonspecific confusion, dehydration, and metabolic acidosis.
Patients with acute ingestion and serum levels greater than _____ mg/L (120 mg/dL) require hemodialysis.
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What is the mechanism of toxicity for NSAIDs?
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What is one potential effect of dapsone overdose?
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There is a specific antidote for most NSAID overdoses.
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A toxic dose of isoniazid may occur after ingestion of _____ g.
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Match the following medications with their corresponding uses:
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Activated charcoal can be used for decontamination in cases of overdose.
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What is the minimum toxic dose of quinine in adults?
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What is Dextromethorphan commonly used for?
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Which of the following are symptoms of mild intoxication with Dextromethorphan? (Select all that apply)
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Dextromethorphan has analgesic properties.
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What is the usual recommended adult daily dose of Dextromethorphan?
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What is the toxic dose of Phenylpropanolamine (PPA)?
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Which of these agents is a methylxanthine used for asthma treatment?
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Corticosteroids are primarily used for treatment during acute asthma attacks.
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Salicylates are primarily used for their analgesic and anti-________ properties.
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What is the antidote for acetaminophen poisoning?
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Which of the following can cause Reye's Syndrome when taken by children?
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What are the side effects of Chronic Therapeutic INH Use?
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What is the natural pacemaker of the heart?
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Type I Anti-arrhythmic Drugs inhibit fast sodium channels and act on phase _____ of the action potential.
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What is a common use of Beta-adrenergic blockers?
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Type II anti-arrhythmic drugs block potassium channels.
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What condition results from excessive ingestion of beta-blockers?
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Which drug is NOT an example of a Type Ia anti-arrhythmic drug?
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Match the following drugs with their classification:
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What is a potential side effect of amiodarone?
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Calcium channel blockers are used to treat hypertension.
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The main effect of Calcium channel blockers is _____ on cardiac contractility.
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What is a common clinical effect of vasodilators?
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Which of the following is a side effect of Type III anti-arrhythmic drugs?
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Study Notes
Respiratory Drugs Overview
- Dextromethorphan is an opioid derivative, commonly found in OTC cough and cold medicines, with antitussive properties but no analgesic or addictive effects.
- Common combination products include Nyquil, Robitussin DM, and Triaminic DM.
Dextromethorphan
- Effective dose: 60-120 mg/d for adults; 30 mg/d for children (2-5 years).
- Toxic symptoms occur at doses exceeding 10 mg/kg, with mild intoxication leading to clumsiness, ataxia, nystagmus, and hallucinations.
- Severe effects from overdose may include stupor, coma, respiratory depression, and seizures.
- Mechanism of toxicity involves NMDA receptor antagonism and increased serotonin levels, which can lead to serotonin syndrome, particularly when combined with MAOIs.
PPA and Related Decongestants
- PPA is an appetite suppressant that can cause hemorrhagic stroke; toxicity occurs at doses 2-3 times higher than therapeutic levels.
- Phenylephrine and ephedrine, both sympathomimetic agents, are commonly used for nasal decongestion.
- Main toxic effects include hypertension, headache, confusion, seizures, and possible myocardial infarction.
Treatment for PPA Toxicity
- Management includes emergency treatment for hypertension and arrhythmias, with caution against using beta-blockers without vasodilators.
- Decontamination options include activated charcoal and urinary acidification.
Theophylline
- A methylxanthine used in asthma management; available as oral medications and IV infusions (aminophylline).
- Overdose can lead to symptoms such as tremor, anxiety, tachycardia, metabolic acidosis, and seizures, especially at serum levels above 100 mg/L.
- Mechanism of action includes phosphodiesterase inhibition, leading to increased cAMP and bronchodilation.
Bronchodilators
- Beta-agonists (e.g., Albuterol, Salbutamol) can be short-acting or long-acting, effective in managing acute asthma and nocturnal attacks.
- Anticholinergic drugs (e.g., Ipratropium, Tiotropium) block muscarinic receptors, preventing bronchoconstriction and offering benefits for COPD.
- Side effects of anticholinergics include dry mouth and constipation.
Anti-inflammatory Agents
- Mast cell stabilizers (e.g., Cromolyn sodium) prevent bronchoconstriction by stabilizing mast cell membranes.
- Lipoxygenase inhibitors (e.g., Zileuton) inhibit leukotriene synthesis; monitoring liver function is important due to hepatotoxicity.
- Leukotriene receptor blockers (e.g., Montelukast) prevent LTD4 binding, reducing airway inflammation.
- Corticosteroids (e.g., Budesonide, Fluticasone) effectively regulate inflammation, with potential side effects including oral thrush.
Acetaminophen Overview
- Acetaminophen (Tylenol) is a common analgesic that is a weak inhibitor of COX-1 and COX-2, leading to liver toxicity at high doses.
- Toxicity occurs above 140 mg/kg in children or 6 g in adults, resulting in elevated transaminase levels and possible hepatic necrosis.
- Diagnosis involves measuring acetaminophen levels and monitoring liver function tests; antidote includes N-acetylcysteine for overdose.
- Overdose may result in serious complications such as hepatic encephalopathy and acute renal failure, particularly in pregnant women.### Acetaminophen Toxicity
- Children under 10-12 years have reduced susceptibility due to less cytochrome P-450 involvement in metabolism.
- Chronic alcohol users and those with induced cytochrome P-450 have lower safety margins, leading to higher poisoning risk by generating more toxic metabolites.
- N-acetylcysteine is the antidote, providing 140 mg/kg orally to replenish glutathione levels.
- Acute toxicity results from NAPQI accumulation due to decreased glutathione, causing hepatotoxicity.
- Decontamination involves activated charcoal, administered promptly in prehospital settings.
- A fatal dose of acetaminophen can be as low as 15 grams, causing hepatocyte death and potentially acute renal necrosis.
Salicylates
- Salicylates serve as analgesics and anti-inflammatories, with 1981 marking the recognition of aspirin for heart attack prevention.
- Aspirin (81mg) launched in 1998 and recognized in 2002 by Health Canada for heart attack prevention.
- Overdose was historically a leading cause of childhood accidental death prior to child-resistant packaging.
- Chronic intoxication in arthritis patients manifests at serum levels of 100-300 mg/L; levels exceeding 600 mg/L indicate severe toxicity.
- Mixed respiratory alkalosis and metabolic acidosis are common signs of salicylate toxicity, necessitating monitoring of blood gases and electrolytes.
Management and Treatment of Salicylate Toxicity
- Sodium bicarbonate is used as an antidote to counteract acidemia.
- Activated charcoal can be utilized in prehospital and hospital settings for decontamination.
- Urinary alkalinization enhances salicylate excretion by creating a basic environment, thus ionizing the drug for easier elimination.
- Hemodialysis is effective for removing salicylates in severe cases, especially if serum levels exceed critical thresholds.
NSAIDs Toxicity
- Overdose of NSAIDs typically leads to mild gastrointestinal symptoms but can escalate to significant CNS and renal dysfunction.
- Most NSAID overdoses do not have a specific antidote; symptoms are generally self-limiting.
- The common mechanism of toxicity relates to the inhibition of cyclooxygenase (COX), affecting gastric mucosa and renal blood flow.
- Severe reactions may include seizures, renal failure, and hepatic dysfunction.
- Decontamination can include activated charcoal, and supportive care measures are crucial to address seizures and hypotension.
Chemotherapeutic and Antimicrobial Drugs
- Chemotherapeutic agents like dapsone, amantadine, quinine, chloroquine, and isoniazid have specific toxicities and management protocols.
- Antibiotics, such as co-trimoxazole, are associated with allergic reactions or overdose risks, with rare severe toxicity from acute ingestions.
- Monitoring serum levels is crucial for aminoglycosides and vancomycin due to their potential toxic effects.
- Leucovorin is used as an antidote for trimethoprim poisoning, counteracting its folic acid antagonist effects.
Conclusion
- Drug toxicity presents varied clinical manifestations that require specific management strategies.
- Prompt treatment and identification of the offending agent are critical for successful outcomes in cases of overdose.### Leucovorin
- A derivative of folic acid that restores normal folate levels.
- Administered intravenously after overdose in hypersensitive individuals.
- Life-threatening reactions can occur from subtherapeutic doses.
Trimethoprim and Dapsone
- Trimethoprim inhibits dihydrofolate reductase.
- Dapsone is an antibiotic for leprosy and prophylactic treatment in AIDS patients.
- Overdosing on Dapsone can cause methemoglobinemia, requiring methylene blue as treatment.
Mechanism and Effects of Dapsone Toxicity
- Dapsone metabolites oxidize hemoglobin's ferrous iron to ferric state, inducing methemoglobinemia.
- Sulfhemoglobinemia results from sulfate addition to hemoglobin ring, with no antidote available.
- Hemolysis may be delayed after ingestion; Heinz bodies can be observed.
Clinical Presentation of Dapsone Overdose
- Symptoms include cyanosis, dyspnea, and potential hemolytic anemia.
- Peak plasma levels occur between 4 to 8 hours post-ingestion.
- Average half-life after therapeutic dose is 30 hours; can extend to 77 hours after overdose.
Treatment of Dapsone Poisoning
- Emergency measures include activated charcoal to interrupt enterohepatic recirculation.
- Methylene blue indicated for methemoglobinemia when levels exceed 15%.
- Enhanced elimination through repeated activated charcoal can significantly reduce half-life.
Amantadine
- Effective for treating Parkinson’s disease and cocaine addiction, known for its dopamine modulation.
- Has anticholinergic properties; overdose can lead to severe toxicity in the elderly.
Clinical Presentation of Amantadine Toxicity
- Symptoms include hallucinations, tremors, slurred speech, and dysphoria.
- Toxicity linked to serum levels surpassing 1.5 mg/L.
Treatment of Amantadine Overdose
- No known antidote; supportive care is crucial.
- Manage tachyarrhythmias with beta-blockers.
- Activated charcoal is indicated for decontamination, though hemodialysis is ineffective.
Quinine
- Extracted from the bark of cinchona tree, used for malaria and nocturnal muscle cramps.
- Toxic doses can lead to retinal toxicity and other serious side effects.
Clinical Presentation of Quinine Toxicity
- Initial symptoms include nausea, vomiting, and cinchonism; severe cases present with ataxia and respiratory failure.
- Retinal toxicity manifests within 9-10 hours of overdose, leading to blurred vision and potential blindness.
Treatment of Quinine Overdose
- Emergency measures involve hypertonic sodium bicarbonate for cardiotoxicity and activated charcoal for gastrointestinal decontamination.
- Mefloquine can cause severe neurological symptoms and cardiovascular effects.
Chloroquine and Aminoquinolines
- Used for malaria and rheumatoid arthritis; overdose presents with cardiac toxicity and CNS effects.
- Chloroquine can lead to hemolytic anemia and methemoglobinemia in susceptible individuals.
Isoniazid (INH)
- A key bactericidal agent for tuberculosis related to significant metabolic effects upon overdose.
- Competes with vitamin B6, resulting in seizures and lactic acidosis in acute cases.
Treatment of Isoniazid Overdose
- Pyridoxine (vitamin B6) is the antidote for diazepam-resistant seizures.
- Activated charcoal is effective; do not induce vomiting due to seizure risk.
Key Considerations for Toxicity Management
- Regular monitoring of electrolytes, renal function, and metabolic status is critical across all toxicities.
- Specific histories of ingestion and clinical presentations are vital for accurate diagnosis and treatment.
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Description
This quiz covers Respiratory Drugs including Dextromethorphan, PPA and related decongestants, Theophylline and Anti-inflammatory Agents. It's a part of PHCT Midterms, Week 6.
