Pharmacology Drugs Affecting The CNS PDF

WEEK 7: DRUGS AFFECTING THE CNS NCMA 216 - PHARMACOLOGY 2ND YEAR - BS NURSING (MIDTERMS) Padayon, SN. Drugs affecting the nervous system alter its functions. A These conditions occur due to increased excitatory...

WEEK 7: DRUGS AFFECTING THE CNS NCMA 216 - PHARMACOLOGY 2ND YEAR - BS NURSING (MIDTERMS) Padayon, SN. Drugs affecting the nervous system alter its functions. A These conditions occur due to increased excitatory thorough review of the Anatomy and neurotransmitters causing rapid brain impulse Physiology of the Central Nervous System and Autonomic conduction causing restlessness, irritability, loss of System would help students understand the mechanisms of concentration, loss of mental focus and sympathetic actions of drugs. The functional unit, neurons' basic function responses like palpitations, tremors, diaphoresis, is impulse transmission which happens by electrical and increase breathing and increase blood pressure. chemical process. Electrical transmission of impulses happen by action potential and chemical processes DRUGS FOR ANXIETY ARE CALLED ANXIOLYTIC make use of neurotransmitters to achieve its functions. DRUGS OR SEDATIVE HYPNOTIC AGENTS ★ Mechanism of action CENTRAL NERVOUS SYSTEM ○ to enhance the effect of GABA (Gamma Brain & Spinal Cord – A very important structure Amino Butyric Acid), an inhibitory of the CNS is its protective mechanisms that not all neurotransmitter to decrease impulses in chemicals can pass through it, this affects the the synapses of the brain, therefore pharmacodynamics of drugs because some of them decreasing conduction of rapid impulses cannot penetrate the CNS. One vital protective causing symptoms of anxiety. structure is the Blood Brain Barrier (BBB). This represents a therapeutic challenge to drug ★ Drug Classifications treatment of brain related disorders because a large Barbiturates – drug action is to enhance GABA percentage of drugs are carried bound to plasma effect. This is used to be the drug of choice to proteins and are unable to cross the brain. manage anxiety but its depressant effect may cause severe respiratory depression that this is not PERIPHERAL NERVOUS SYSTEM primarily used for anxiety today Autonomic Nervous System & Somatic Nervous ○ Pharmacokinetics: Barbiturates are System – Synapses made by the peripheral absorbed well, reaching the peak levels in nervous system conduct impulses that are chemical 20 to 60 minutes. It is metabolized in the in nature. These neurotransmitters have specific liver and excreted in the urine receptors in the neural membrane tos facilitate ○ Contraindications and Cautions: conduction of nerve impulses. Drugs may act in the Barbiturates are more addicting than other nervous system to either stimulate or block the anxiolytic drugs. May cause severe CNS receptors to correct alterations in the nervous depression and respiratory dysfunction. functions. Contraindicated in pregnant women and Neurons conduct impulses by Action Potential, the clients with hepatic and renal dysfunction rapid change in the membrane potential, this ○ Adverse Effects: CNS depression, happens by movement of sodium into the cells paradoxical excitement, anxiety and causing depolarization and potassium out of the hallucinations. Gastrointestinal signs and cells to cause repolarization. This movement of ions symptoms like nausea, vomiting, facilitated by channels in the cell membranes will be constipation, diarrhea and epigastric pain. acted upon by drugs to correct changes in the Cardiovascular effects include nervous system causing disease process. bradycardia, hypotension and syncope ○ Examples: Phenobarbital, Secobarbital, CLASSIFICATIONS OF DRUGS AFFECTING THE CNS Amobarbital 1. Anxiolytic and Hypnotic Drugs Benzodiazepines – drug action is to enhance ❖ Anxiety is a feeling of tension, nervousness, GABA effect to cause inhibition of impulse apprehension or fear that usually involves transmission. unpleasant reactions to a stimulus, whether actual ○ Pharmacokinetics: this is well absorbed or unknown. Anxiety is classified as mild, moderate, in the GIT with peak levels achieved in 30 severe and panic. Mild anxiety is normal as it helps minutes. This is lipid soluble and well the person to have a wider perspective and focus distributed in the body crossing the BBB, on certain activities but increasing anxiety may placenta and breast milk. Metabolized in cause restlessness and increase sympathetic stress the liver and excreted in the urine reaction which may cause physical symptoms of the ○ Contraindications and Cautions: sympathetic stress reactions. When anxiety Contraindicated in Clients with allergy to becomes moderate, there is a need for drug benzodiazepines, psychosis, clients with treatment. acute narrow angle glaucoma, shock, ❖ Sedation is the loss of awareness and reaction to acute alcohol intoxication which may environmental stimuli. Hypnosis is severe sedation. exacerbate the depressant effects of the  drugs. Contraindicated in pregnancy as excreted in the urine. this is known to possibly cause cleft lip or palate, inguinal hernia, cardiac defects, Beta Blockers – Decreasing sympathetic microcephaly or pyloric stenosis if taken Propranolol effect to lessen signs and during the first trimester. Caution should be Metoprolol symptoms of anxiety. used in the elderly or debilitated patients an those with hepatic and renal functions ★ Nursing Considerations ○ Adverse Effects: Sedation,drowsiness, ○ Do not administer intra arterially because depression, lethargy, anticholinergic of possible serius arteriospasm and effects like drying of mount, constipation, gangrene may develop orthostatic hypotension, urinary retention, ○ Do not mix IV drugs with other drugs dysrhythmias, blood dyscrasias and ○ Give parenteral forms if oral forms are not phlebitis. Withdrawal syndrome may occur feasible and switch to oral which is safer with abrupt cessation characterized by ○ Give IV drugs slowly to avoid hypotension nausea, headache, vertigo, malaise and effects headache. ○ Promote safety measures ○ Examples: Diazepam, Lorazepam, ○ Monitor hepatic and kidney function Clonazepam ○ Taper dose of drugs gradually Non - Benzodiazepines - other drugs used for ○ Provide comfort measures to help patient anxiety that do not fall under Benzodiazepine tolerate the effects of drugs DRUGS DESCRIPTIONS ○ Provide thorough health teaching about Rapid onset of confusion (severe form of alcohol withdrawal) drug effects and adverse reactions Paraldehyde Old drug used for Delerium ○ Offer support and encouragement Tremens, seizures, ○ For overdose of Benzodiazepine, absorbed and metabolized Flumazenil must be ready as its antidote. in the liver. It has a distinctive odor and cannot be stored 2. Antidepressant Drugs in plastic containers. Feelings of sadness are normal and expected after a tragic event in life. This is an expected Meprobamate An old drug used to response to a stressor. Since this is a normal manage anxiety for 4 process, many people experiencing severe sadness months, works in the may develop a depressive disorder unrecognized. limbic system metabolized People fail to distinguish the normal process of in the liver and excreted in the urine. grieving with a major depressive disorder. Depression being an affective disorder is Chloral hydrate Frequently used to produce recognized by its clinical manifestations such as (Night) nocturnal sedation or (before surgery) sleep disturbances, they have little energy, inability preoperative to perform daily activity. They may describe sedation. Unknown overwhelming feelings of sadness, despair, mechanism of hopelessness and disorganization. action, absorbed in the GIT, metabolized in the liver and Pharmacology explains depression by Biogenic excreted in the urine. Amine Theory. This theory explains that depression occurs due to decreasing neurotransmitters, Zolpidem Used to treat insomnia, norepinephrine, serotonin and dopamine. Metabolized in the liver and When impulses travel across the synapses, excreted in the urine. neurotransmitters are released into the synapse, they bind in the receptors in the post synaptic Antihistamines - Used or its drowsiness neural membrane and help impulse to be Diphenhydramine ( effect in anxiety. With Benadryl) Promethazine ( anticholinergic effect. conducted. After which, neurotransmitters are Phenergan) Used during preoperatively removed by enzymes or they may go back to the or postoperatively to presynaptic neuron: decrease use of narcotics. ○ In the limbic system which is the area responsible for overall emotion and Buspirone No sedative,anticonvulsant, behavior, there are three neurotransmitters or muscle relaxant being released, Norepinephrine, Serotonin properties, unknown mechanism of action, and Dopamine. After impulse is reduces anxiety without transmitted across the synapse, and many CNS effects. enzyme called MonoAmine Oxidase will Absorbed in the GIT, remove them. Some however may go back metabolized in the liver an to the pre synaptic neuron the process BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 2  called reuptake of Neurotransmitters. If abnormal rhythms, myocardial they are not available in the synapse, there infarction, anticholinergic effects will be no more impulse transmission. like drying of the mouth, ○ Let us go back to Biogenic Amine Theory constipation, urinary retention which explains that depression results Remember Mnemonics: from decreasing neurotransmitter in the C – Cardiovascular effects limbic system which may happen due A – Anticholinergic effects possibly to: S – Sedation 1. Overused of neurotransmitters ( H – Hypotension or Hypertension Norepinephrine, Dopamine and MonoAmine Oxidase Inhibitors Serotonin) ○ These drugs inactivate the enzyme MAO 2. Increase effect of MonoAmine to increase the neurotransmitters in the Oxidase ( MAO ) enzyme synapses. 3. Increase reuptake of ○ Pharmacokinetics: absorbed in the GIT, neurotransmitter back to reaching peak levels in 2 – 3 hours, presynaptic neuron metabolized in the liver and excreted in the ○ If we know the problem in the limbic urine. They pass the placenta and breast system is decreasing neurotransmitters, milk and are not used in pregnancy. then we need to increase them and make ○ Contraindications and Cautions: them stay in the synaptic cleft. Drugs for Contraindicated in clients with hypertension may achieve its therapeutic cardiovascular disease, hepatic and renal effect within 2 – 4 weeks from its oral disease. Caution should be used in intake. psychiatric patients ○ Adverse Effects: More adverse effects DRUGS FOR DEPRESSION ARE CALLED than other antidepressant drugs. ANTIDEPRESSANT DRUGS Dizziness, excitement, nervousness, ★ Mechanisms of action mania, hyperreflexia, tremors, confusion, ○ Inhibit the enzyme MonoAmine Oxidase insomnia, agitation and blurred vision. (MAO) Liver toxicity, Cardiovascular toxicity. ○ Inhibit Reuptake of Neurotransmitters Anticholinergic effects ○ Drug – Drug interaction: Drug interaction ★ Drug Classifications with other antidepressant drugs include ○ Tricyclic Antidepressants (TCA) – inhibit hypertensive crisis, coma and severe presynaptic reuptake of neurotransmitter, convulsion. A period of 6 weeks should norepinephrine and serotonin, which leads elapse after stopping SSRI and beginning to accumulation of these neurotransmitters MAOI. in the synaptic cleft and increased ○ Drug – Food Interactions: Tyramine – rich stimulation of postsynaptic receptors. food which normally broken down by MAO Pharmacokinetics: it is enzymes in the GIT maybe absorbed in absorbed in the gastrointestinal high concentration in the presence of tract, reaching the peak in 2 to 4 MAOI and may cause hypertensive crises. hours. Widely distributed in the ○ Examples: Isocarboxazid, Phenelzine, tissue including the brain. Tranylcypromine Metabolized in the liver and Selective Serotonin Reuptake Inhibitors (SSRI) – excreted in the urine. They cross these drugs specifically block the reuptake of the placenta and breast milk. serotonin with little or no effect on Norepinephrine. Contraindications and Caution: SSRIs do not have the many adverse effects of Contraindicated to those with TCAs and MAOIs known allergy to TCA. Clients ○ Indications: Depression, Obsessive with recent myocardial infarction Compulsive Disorders (OCD) Panic because of its cardiovascular attacks, Bulemia, Post Traumatic Stress effects. Caution should be used in Disorder (PTSD) clients with Gastrointestinal and ○ Pharmacokinetics: well absorbed in the Genitourinary tract disorders. The GIT, metabolized in the liver and excreted presence of hepatic and renal in the urine or feces. SSRIs are associated impairment increases toxicity of with congenital abnormalities. They the drugs. passed the placenta and the breastmilk Adverse Effects: CNS effects ○ Contraindication and Caution: Those like sedation, hallucinations, with allergy to SSRIs, pregnancy and fatigue, cardiovascular effects, lactation. unstable blood pressure, BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 3  ○ Adverse Effects: CNS effects like making them more specific drugs for headache, drowsiness, dizziness, Psychotic disorders. insomnia, anxiety, tremor, agitation and seizures. Anticholinergic effects on the ★ Drug Classifications gastrointestinal tract and genitourinary ○ Typical Antipsychotic drugs: Older tract. drugs, they are less potent and associated Examples: Fluoxetine, Sertraline, with more adverse effects Paroxetine Examples: Chlorpromazine, Fluphenazine, Thioridazine, ★ Nursing Considerations Haloperidol ○ Limit drug access to potentially suicidal ○ Typical Antipsychotic drugs: Older patients to decrease the risk of overdose drugs, they are less potent and associated ○ Monitor the patient for 2 – 4 weeks to with more adverse effects ascertain onset and full effects Examples: Chlorpromazine, ○ Monitor blood pressure and orthostatic Fluphenazine, Thioridazine, blood pressure carefully Haloperidol ○ Monitor liver function ○ Pharmacokinetics: Antipsychotic drugs ○ Withhold medication dose in client with are erratically absorbed in the GIT, severe headache that may due to severe metabolized in the liver and excreted in the hypertension and cerebrovascular effects bile and urine. Widely distributed in the ○ Have phentolamine or another adrenergic tissues, being released up to 6 months blocker for hypertensive crisis after they are discontinued. Drugs cross ○ Provide comfort measures to help the the placenta and breast milk so they are client tolerate drug effects not given to pregnant and lactating ○ Provide list of food that is low or no mothers tyramine to clients on MAOI therapy ○ Contraindications and Cautions: ○ Offer support and encouragement to help Contraindicated in patients with patients cope with the disease and drug Parkinson’s disease, cardiovascular regimen disease, severe hypotension and bone marrow suppression 3. Psychotherapeutic Drugs ○ Adverse Effects include Anticholinergic Mental disorders have several classifications. For effects like drying of the mouth, this course, discussion include only drugs used for constipation and urinary retention, Schizophrenia and Mania, two of the most common Sedation effect, Orthostatic hypotension psychiatric disorders. and extra pyramidal symptoms. Schizophrenia is the most common type of Remember the mnemonics ASHE. psychotic disorder. This prevents an individual from These are the most common adverse functioning in society. Some clinical manifestations effects of antipsychotic drugs which are include, hallucinations, delusions, paranoia, speech manifesting more in typical antipsychotic abnormalities and affective problems. than atypical antipsychotic drugs Mania is associated with Bipolar illness. Mania is A – Anti cholinergic effect characterized by periods of extreme overactivity S – Sedation and excitement H – Hypotension E – Extra pyramidal Symptoms Drugs for mental disorders are called Psychotherapeutic ○ Parkinson’s like syndrome, Dystonia, drugs. Drugs for Schizophrenia are called Antipsychotic Akathisia, Tardive dyskinesia these Drugs and drugs for Mania are called Anti Manic Drugs. adverse reactions happen because of dopamine blocking effect in the basal Antipsychotic drugs ganglia altering its function of coordination ★ Mechanisms of Action and fine motor function. ○ Typical Antipsychotic drugs – block Dopamine receptors in the limbic system, Other adverse effects may include respiratory distress like in the reticular activating system and the laryngospasms, bronchospasms and dyspnea. Bone marrow brain. This group of antipsychotic may suppression and blood dyscrasia are seen in some patients block all dopamine receptors including those not associated with psychoses ★ Nursing Considerations ○ Atypical Antipsychotic drugs – block ○ Do not allow patients to crush or chew the Dopamine and Serotonin receptors. This tablet as it decreases absorption of the group will lock only the receptors of drugs Dopamine and Serotonin which are ○ Monitor for orthostatic hypotension responsible for occurrence of psychosis BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 4  ○ Consider warning the patient or the ★ Nursing Considerations on administration of patient’s guardian on the risk of tardive Lithium dyskinesia ○ Daily monitoring of lithium serum levels ○ Monitor CBC to check signs of bone ○ Give the drug with food to alleviate GI marrow suppression irritation ○ Provide positioning of legs to decrease ○ Ensure that the patient have adequate discomfort of dyskinesia intake of salt and fluid ○ Provide sugarless candies for drying of the ○ Monitor closely especially during the initial mouth stage of therapy Arrange for small and ○ Encourage the patient to void before taking frequent meals with sugarless lozenges for the dose if urinary retention is a problem drying of mouth ○ Provide safety measures such as side rails ○ Provide safety measure like side rails and and assistance in ambulation if there are assistance with ambulation if CNS effects CNS effects occur to prevent potential injury ○ Provide vision examination to determine ○ Offer support and encouragement or help ocular changes patient cope with drug regimen ○ Conduct thorough health teaching on the effects and adverse effects of the drugs 4. Anti-Seizure Drugs ○ Offer support and encouragement to help Seizure is a collection of different syndromes patients cope with their drug regimen characterized by abnormal and excessive impulse transmission in the brain. Seizures may be primary AntiManic Drug - LITHIUM or secondary. Primary seizure disorder has no ★ Mechanism of Action known cause; this is often called Epilepsy. ○ Lithium alters sodium transport in the Secondary Seizure may be caused by nerve and muscle, inhibits the release of Cerebrovascular accident, Infections, Brain Tumor, norepinephrine and dopamine slightly and Traumatic Brain Injury, Fever and a lot more decreases intraneuronal content of second conditions that may alter impulse transmission in messengers. The last action may modulate the brain. Seizure and Convulsion are not impulses to control hyperactive state in synonymous. Convulsion is seizure manifesting mania Very excited or manic motor symptoms like tonic clonic seizure. All Pharmacokinetics: Lithium is absorbed in the GIT. convulsions are seizures but not all seizures are It slowly crosses the BBB. Dehydration and sodium convulsions. depletion may cause the kidneys to reabsorb more Seizure is further classified into Generalized and Lithium thus increasing serum levels and toxicity. Partial Seizure. Generalized seizure begins in one Lithium crosses the placenta and breastmilk. area of the brain and rapidly spreads to both Contraindications and Cautions: Contraindicated hemispheres of the brain. to those with allergy to the drug, dehydration, Examples of generalized seizure include Tonic – hyponatremia and leukemia Clonic Seizure formerly known as Grand Mal Adverse Effects: Toxicity associated with serum Seizure. Partial seizures or focal seizures involve level of Lithium. ( Therapeutic level 0.6 – 1.2 one area of the brain and do not spread throughout mmol/L) the entire organ. The presenting symptoms depend ○ Serum level less than 1.5 mmol/L CNS on exactly where the excessive electrical discharge problems including lethargy, slurred is occurring in the brain. Samples include Partial speech, muscle weakness, fine tremor; Seizure and Complex Seizure. polyuria, beginning gastric toxicity The problem of seizure is excessive impulse ○ Serum level 1.5 – 2 mmol/L Intensification transmission in the brain, so the action of the drug of the above plus ECG changes is to decrease impulse transmission, anti seizure ○ Serum levels of 2.0 – 2.5 drugs cause CNS depression. mmol/LProgression of CNS symptoms to ataxia, hyperreflexia and seizure, ★ Mechanisms of Action hypotension 1. Suppressing sodium influx or ○ Serum levels more than 2.5 mmol/L depolarization in the neuron complex multi organ toxicity and death 2. Suppressing calcium influx, preventing electric current generated by calcium ions ★ Other drugs used for Mania 3. Increasing the action of the Gamma Amino ○ Aripiprazole – atypical antipsychotic drug Butyric Acid ( GABA ) an inhibitory ○ Lamotrigine – anticonvulsant drug neurotransmitter in the brain ○ Olanzapine – atypical antipsychotic drug The figure shows how impulses are transmitted across the ○ Quetiapine – atypical antipsychotic drug synapse. Action potential happen by sodium influx and potassium efflux, calcium channels open causing release of calcium that generate electrical activity and BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 5 neurotransmitters both excitatory and inhibitory regulate used for Generalized Tonic – impulse transmission. Excitatory neurotransmitters allow Clonic Seizure impulses to travel while inhibitory neurotransmitters stop ○ Benzodiazepines – enhance GABA impulses. effect. (Refer to Anxiolytic Drugs for detailed discussion and examples) The mechanisms of action of anti seizure drugs occur in the Indications: For status neuronal synapse. Drugs for Seizures are called Anti – epilepticus and benign febrile seizure drugs or Anti – convulsive drugs (Anticonvulsant seizure. Diazepam is not used for drugs) or Anti – Epileptic Drugs. long term treatment of seizures. Clonazepam is good for ★ Drug Classifications treatment of Petit Mal Seizure ○ Hydantoins – inhibit sodium influx or and Myoclonic Seizure depolarization along the nerve fiber. ○ Succinimides – enhanced effect of Pharmacokinetics: Hydantoinsa GABA, an inhibitory neurotransmitter. are absorbed in the GIT.. It is Examples: Ethosuximide the drug highly protein bound up to 95%. A of choice for Petit – Mal or decrease in serum albumin or Absence Seizure with relative few proteins increases free phenytoin adverse effects than other anti serum levels. Average half life is seizure drugs. Methosuximide 24 hour. ○ Valproate or Valproic Acid – reduces Hydantoins are metabolized to electrical activity by suppressing calcium inactive metabolites and excreted influx and enhancing GABA effects the in the liver. Hydantoins are less drug of choice for treating myoclonic sedating than Barbiturates and seizure Benzodiazepines. ○ Other anti- seizure drugs include Adverse Effects: Neurologic and Carbamazepine, Gabapentin, Lamotrigine, psychiatric effects which include and Levetiracetam. Topiramate. Some of slurred speech, confusion, these drugs used for partial seizure may depression. Low platelet count also be used for treatment of neuropathic and WBC may happen and pain like Carbamazepine is used for gingival hyperplasia (overgrowth treatment of Trigeminal Neuralgia. of gum tissue or reddened gums that easily bleeds). ★ Nursing Considerations: Hyperglycemia and less severe ○ Administer the drug with food to alleviate adverse effects such as nausea, GI irritations vomiting, constipation, ○ Monitor CBC to detect possible bone drowsiness, headache and marrow suppression alopecia ○ Evaluate therapeutic blood level to prevent Drug – Drug interactions: toxicity Hydantoins must not be taken ○ Provide safety measures with other anti seizure drugs ○ Provide thorough health teaching, because it may increase its CNS including drug name, prescribed dosage depressant effects. Increased and avoidance of adverse effects effects of Hydantoins happen in ○ Suggest that clients wear Medic Alert combination with Aspirin, Bracelet to alert health care worker about anticoagulants, Barbiturates, the use of antiepileptic drugs Rifampicin and chronic ingestion ○ Offer support and encouragement to help of ethanol. Decreased Hydantoins the patient cope with the drug regimen. absorption occurs when combined with Antacids, calcium 5. Anti – Parkinson’s Drugs preparations, sucralfate and Parkinson’s Disease is a degenerative disorder of some anticancer drugs. the central nervous system. There is no known Examples: cause. This is common among elderly 60 years old Phenytoin,Fosphenytoin, Ethotoin and above. The disease is characterized by ○ Barbiturates - enhanced GABA effect. degeneration of the substantia nigra in the midbrain. These drugs are highly sedating and they A dopamine secreting neurons in the brain. may cause severe CNS depression. (Refer Therefore there is a tremendous decrease of to Anxiolytic Drugs for detailed discussion ) dopamine in the brain especially affecting the basal Indications: Anxiety, General ganglia. The basal ganglia is responsible for Anesthesia and most commonly coordinating fine motor movement of the body. Alterations in the basal ganglia function result in BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 6  lack of coordination, tremors, rigidity and with MAOI may increase bradykinesia. The neurons of the basal ganglia hypertensive crisis. The function normally when there is a balance between combination of levodopa with excitatory and inhibitory neurotransmitters. Vitamin B6 and phenytoin and Dopamine in the basal ganglia acts as the inhibitory dopamine antagonists may lead neurotransmitter and Acetylcholine produced by to decreased effect of higher neurons in the cerebral cortex act as dopaminergic drugs. excitatory neurotransmitter. Examples In Parkinson’s disease an imbalance of ○ Levodopa – a precursor of neurotransmitters, decreased dopamine and Dopamine. Once levodopa enters increased acetylcholine results to clinical the BBB, it becomes dopamine manifestations causing incoordination for and will replace the loss of unconscious muscle movements including those dopamine. Dopamine itself that control position, posture and movement cannot pass the BBB so a Anti – Parkinson’s drugs should balance the effects precursor called Levodopa is of the neurotransmitters. To increase Dopamine used. When this drug was effect and to decrease Acetylcholine effect should developed, there was a dramatic control symptoms of Parkinson’s Disease. These reduction in the signs and Drugs do not cure the disease but control the symptoms of Parkinson’s symptoms, hence the use is for palliative treatment. disease, however it was found out later that levodopa can be ★ Mechanisms of Action destroyed by and enzyme called 1. To increase dopamine effect dopa decarboxylase before they 2. To suppress acetylcholine effect cross the BBB resulting to decreasing the level of levodopa ★ Drug Classifications that may cross the BBB. This is Dopaminergic drugs – increase the effect the reason why another drug is of Dopamine at the receptor sites by combined with levodopa. This is increasing the levels of dopamine in the Carbidopa. This drug cannot substantia nigra or directly stimulating the increase the level of dopamine in receptors the brain but it inhibits the ○ Pharmacokinetics: These drugs enzyme, dopa decarboxylase, are absorbed in the GIT, therefore allowing more levodopa metabolized in the liver and to pass the BBB. A combination excreted in the urine. They cross of levodopa and carbidopa the placenta and the breast milk (Sinemet) is still the best drug for ○ Contraindication and Caution: Parkinson’s disease. Contraindicated to clients with ○ Amantadine is a drug that can allergy to the drugs and glaucoma increase the release of dopamine. as the drug can exacerbate This drug can be effective as long glaucoma. Caution should be as there is a possibility of more used with any condition that could dopamine release. be exacerbated by dopamine ○ Bromocriptine acts as a direct receptor stimulation such as dopamine agonist on dopamine cardiovascular disease, bronchial receptor sites in the substantia asthma, peptic ulcer disease, nigra. urinary tract obstruction and Anticholinergic drugs – oppose the psychiatric disorders. effects of acetylcholine at receptor sites in ○ Adverse Effects: CNS effects the substantia nigra. These anticholinergic include anxiety, nervousness, drugs have greater affinity with the headache, malaise, fatigue, receptors of acetylcholine in the CNS than confusion, mental changes, those in the periphery. However, they still blurred vision, muscle twitching block some receptors at the autonomic and ataxia. Peripheral effects nervous system. Blocking the acetylcholine include anorexia, nausea, effect helps to normalize the dopamine – vomiting, diarrhea, constipation, acetylcholine imbalance in the basal cardiac arrhythmias, urinary ganglia. retention and bone marrow Pharmacokinetics: drugs absorbed in the suppression GIT, metabolized in the liver and excreted ○ Drug – Drug interaction. by cellular pathways. They pass the Dopaminergic drugs combined placenta and the breast milk BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 7  Contraindications and Cautions: PARASYMPATHETIC NERVOUS SYSTEM Contraindicated in clients with Parasympathetic nervous system (PNS) comes Gastrointestinal or Genitourinary from the cranio – sacral outflow of the peripheral obstruction. Caution should be used in nervous system. Cranial nerve X, IX, VII, III clients with cardiovascular conditions participate in the cranial flow. Majority of the PNS because of its blocking effect of comes from cranial nerve X ( Vagus nerve ). This is parasympathetic nervous system the only cranial nerve that extends up to the thorax Adverse Effects: Blocking CNS and abdomen to supply the majority of acetylcholine may cause disorientation, parasympathetic innervation, so a vagal stimulation confusion and memory loss. Peripheral is synonymous with parasympathetic innervation. anticholinergic effects include drying of the Sacral nerves also participate in the PNS to supply mouth, constipation, urinary retention and mostly the effectors in the pelvic area like urinary orthostatic hypotension. bladder. Drug – Drug interaction: These drugs The ganglia of the PNS are located near the organ should not be combined with other drugs of innervation. The neurons therefore of the PNS with anti – cholinergic effects like are pre – ganglionic neuron, the neuron from the antipsychotic, anti – depressant drugs. Cranio – sacral outflow to the ganglia and the post – ○ Examples: Diphenhydramine ( ganglionic neuron, the neuron from the ganglia to Benadryl ), Benztropine ( the organ of innervations. PNS is responsible for Cogentin ), Biperiden ( Akineton ) “REST AND DIGEST” involuntary responses of the Trihexyphenidyl ( Artane ) These body drugs are famous for their brand Impulses transmitted across the synapses of the names. Most often used for ganglia are mediated also by the neurotransmitters. treatment of Parkinson’s like In the PNS, the neurotransmitter is Acetylcholine. syndrome, an adverse effect of Receptors for acetylcholine are located in the post antipsychotic drugs. synaptic neuronal membrane. These receptors are called cholinergic receptors. There are 2 types of ★ Nursing Considerations cholinergic receptors Provide sugarless lozenges to relieve ○ Nicotinic Receptors drying of the mouth ○ Muscarinic receptors Give the drugs with caution in hot weather or with exposure to hot environment SYMPATHETIC NERVOUS SYSTEM because of increase risk for heat The division of the autonomic nervous system, prostration Sympathetic nervous system (SNS) from the Give drugs with meals as they may cause thoraco- lumbar outflow, spinal nerves from this GI irritation region send nerve fibers to the sympathetic ganglia Monitor bowel functions located near the CNS, then post ganglionic neurons Establish safety precautions send innervation to the involuntary muscles and Ensure that the patient voids before taking glands and other effectors mostly associated with the drugs if urinary retention is a problem involuntary process in the body. Provide thorough patient teaching about The preganglionic neuron of the SNS is shorter than topics such as the drug name and PNS and the post ganglionic neuron is longer than prescribed dosage, measures help to PNS. SNS is responsible for “FIGHT OR FLIGHT” avoid adverse effects, warning signs that involuntary responses of the body. Impulses may indicate problems and need for transmitted across the synapses also are mediated periodic monitoring and evaluation to by the neurotransmitters. There are two enhance patient knowledge about drug neurotransmitters in the SNS. Acetylcholine and therapy and to promote compliance Epinephrine and Norepinephrine ( Catecholamines ) Offer support and encouragement to help Actylcholine is released by the preganglionic the patient cope up with the disease and neurons, while epinephrine and norepinephrine are drug regimen the neurotransmitters released by the post ganglionic neurons, except for those post ganglionc AUTONOMIC NERVOUS SYSTEM neurons innervating adrenal medulla, pilo arector The division of the peripheral nervous system that muscles, sweat glands and some smooth muscles supply involuntary muscles, glands and other of the blood vessels, they have sympathetic effectors not innervated by the somatic nervous innervations but the neurotransmitter in at the system. Autonomic nervous system is responsible postganglionic neurons is Acetylcholine for all involuntary actions of the body that the Epinephrine and Norepinephrine may also be called person is not aware of. This is divided into two Adrenalin and Noradrenaline respectively or they divisions: are being refered to as catecholamines. Their receptors are called Adrenergic Receptors. BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 8  There are 2 types of adrenergic receptors may occur at the synaptic level ○ Alpha receptors but exact mechanism is unknown ○ Beta receptors Contraindications and Cautions: These drugs enhance DRUGS AFFECTING THE AUTONOMIC NERVOUS parasympathetic effect so must SYSTEM ARE CALLED AUTONOMIC DRUGS not be given to patients with Classifications of Autonomic Drugs hypotension, bradycardia or heart Drugs affecting the PNS are called Cholinergic block, intestinal obstruction and Drugs urinary retention Drugs affecting the SNS are called Adrenergic Adverse effects: These are Drugs related to increased In the study of pharmacodynamics, one action of parasympathetic responses such the drugs is its binding with the receptors that may as bradycardia, diarrhea, urinary stimulate the receptors (drugs are called agonist) incontinence. Increased sweating and drugs that may block the receptors (drugs are may happen because of the called antagonists). If a student is aware of the acetylcholine present in the sweat responses of the PNS and SNS, it would be easier glands. to remember drug actions, they would either Drug – Drug interaction: Effects stimulate the receptors and produce the same effect of these drugs may increase if or block the receptors or inhibit the effects. combined with anticholinesterase Most of the effectors are innervated by both drugs or the indirect acting sympathetic and parasympathetic and in such case cholinergic agonists. the response of the body is opposite. See examples Examples below: Bethanechol – indicated for non – Effectors SNS PNS obstructive urinary retention like in Heart Increase HR Decrease HR neurogenic bladder Carbachol – indicated Lungs Bronchodilator Bronchoconstrict for glaucoma, causing Blood vessels Vasoconstrict Vasodilate pupillary constriction Pilocarpine – indicated for glaucoma, causing Therefore, if a drug stimulates the receptors for pupillary constriction PNS, it is called cholinergic agonist, enhancing PNS ○ Indirect acting cholinergic agonist – this effect so such drug is also referred to as drug increases acetylcholine effect by parasympathomimetic drug. A drug that blocks the inhibiting the action of acetylcholinesterase cholinergic receptors is called cholinergic (an enzyme that removes acetylcholine in antagonist, also called anticholinergic drugs, the synapse. If acetylcholinesterase is not inhibiting PNS response and such drug may also be removed in the synaptic cleft, more referred to as parasympatholytic drug acetylcholine stays in the synapse If a drug stimulates receptors for SNS, it is called stimulating more receptors, thus adrenergic agonist, increasing SNS effect so such enhancing their effects. These drugs are drug is also referred to as sympathomimetic drugs. used for treatment of Myasthenia gravis A drug that blocks the adrenergic receptors and Alzheimer’s disease’ decreases SNS responses called adrenergic agonist or it is also called sympatholytic drugs. MYASTHENIA GRAVIS is an autoimmune disease of the neuromuscular Remember, knowing the responses of the PNS and SNS is junction (NMJ). This is characterized by destruction very important to understand actions of autonomic drugs, of cholinergic receptors at the NMJ that will slow because these drugs would only stimulate or block the down impulses going to the skeletal muscles. This receptors. disease is characterized by the development of Cholinergic drugs – majority of these drugs affect muscle weakness and paralysis. To increase the PNS. junctional transmission, an indirect acting ○ Direct acting cholinergic agonist – directly cholinergic agonist inhibits acetylcholinesterase stimulates the cholinergic receptors to making more acetylcholine present in the junction to increase its effects improve impulse transmission and muscle function. Pharmacokinetics: well These drugs are also called anticholinesterase absorbed with relatively short half drugs. – life. Metabolism and excretion Anticholinesterase drugs for Myasthenia gravis include: BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 9  ○ Edrophonium HCL (Tensilon) – short Provide health teaching on the name of acting anticholinesterase drug used to drugs, its action and adverse effects to diagnose the disease. The action lasts for promote client’s understanding and 10 to 20 minutes. compliance ○ Neostigmine, Physostigmine, Provide emotional support and Pyridostigmine – long acting encouragement to help the patient cope anticholinesterase drugs used for with drug regimen therapeutic purposes. The onset of action Cholinergic antagonist is also being starts 20 to 30 minutes and may last for 3 referred to as an anticholinergic drug or – 6 hours. parasympatholytic. The drugs act to block the cholinergic receptors in the PNS. The ALZHEIMER’S DISEASE drugs may also block some cholinergic is a degenerative disease of the CNS characterized receptors present in the SNS by loss of neurons in the CNS which may slow ○ Pharmacokinetics: The drugs down impulse transmission across the synapses of are well absorbed and distributed. the CNS. One important cause of this is explained Drugs pass the BBB, placenta by loss of acetylcholine receptors in the and breastmilk. The drugs are postsynaptic neurons, like myasthenia gravis, less excreted in the urine receptors mean lesser impulse transmission. So ○ Contraindications and anticholinesterase drugs that inhibit Cautions: The drugs are not acetylcholinesterase enzymes will increase given to patients with known acetylcholine effect and promote impulse allergy to the drugs. Should not transmission in the CNS. Can drugs for myasthenia be used in clients with gravis be used on patients with Alzheimer’s cardiovascular, gastrointestinal or disease? The answer is no simply because those genitourinary conditions because drugs cannot pass the BBB. Therefore, Alzheimer’s they may exacerbate disease will have its own anticholinesterase drugs. anticholinergic effects and worsen Acetylcholinesterase drugs used for Alzheimer’s the conditions. Contraindicated in disease are called Anti Alzheimer’s drugs which clients with glaucoma as the drug include: may cause pupillary dilation and ○ Rivastigmine further increase intraocular ○ Donepezil pressure. Caution is used for ○ Tacrine patients with hepatic or urinary Pharmacokinetics: These drugs are well absorbed impairment. and distributed in the body. Drugs for myasthenia ○ Adverse effects: These are do not pass the BBB. The drugs are metabolized in associated with anticholinergic the liver and excreted in the urine. effects of drugs such as drying o Contraindications and Cautions: The drugs are the mouth, constipation, urinary not given to those with known allergy to the drugs. retention, tachycardia, mydriasis. The drugs may exacerbate bradycardia, diarrhea Drowsiness, confusion and and urinary incontinence insomnia are all related to the Adverse effects: Exacerbation of parasympathetic CNS effects of anticholinergic effects may be seen in the patient such as drugs bradycardia, hypotension and incontinence Examples: ○ Atropine – indicated to decrease ★ Nursing Considerations secretions, treat bradycardia, Properly administer eye medication pylorospasm, ureteral colic, Slow IV administration to avoid severe cause pupil dilation (mydriasis) cholinergic effects indicated as preop drug for Cholinergic agonist oral preparation must cataract extraction. Use as be taken with an empty stomach to antidote for cholinergic crisis decrease nausea and vomiting ○ Dicyclomine – use for Closely monitor vital signs and hyperactive bowel in adults exacerbation of parasympathetic effects ○ Scopolamine – use in motion Provide safety measures sickness, indicated to decrease Monitor patients with Alzeimer’s disease secretion, pupil dilation for progression of the disease. Drugs will not cure the disease Adrenergic receptors have 2 types and subtypes. Monitor patients with Myasthenia gravis for Classification is based on their actual locations in the body. underside or overdose of medication Below are some adrenergic receptor sites and their specific locations in the body BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 10 Types of the Adrenergic Receptors pheochromocytoma as the drugs may 1. Alpha receptors exacerbate the signs and symptoms ○ Alpha 1 receptors Adverse effects: These are all related to ○ Alpha 2 receptors increase SNS response like tachycardia, 2. Beta receptor hypertension, constipation, urinary ○ Beta 1 receptors retention, pupillary dilation ○ Beta 2 receptors Examples: ○ Epinephrine – the drug of choice Study the table below for some important locations of the during CPR, indicated for receptors treatment of shock ○ Dobutamine – used for treatment RECEPTORS LOCATION of congestive heart failure ○ Dopamine – usually given for Alpha 1 receptors Vascular smooth muscles, congestive heart failure and iris, visceral smooth muscles like the urinary cardiogenic shock bladder and iris ○ Norepinephrine – like epinephrine, may be indicated for Alpha 2 receptors CNS neurons, pancreatic cardiac arrest islets 2. Alpha specific adrenergic agonist - these drugs specifically stimulate only the alpha receptors and Beta 1 receptors Myocardium, Kidneys, CNS not the beta receptors neurons Pharmacokinetics: these drugs are well Beta 2 receptors Visceral smooth muscles absorbed and distributed, reaching peak like in the lungs, some levels in 20 to 45 minutes. These drugs vascular smooth muscles, are metabolized in the liver and excreted in CNS neurons the urine Contraindications and Cautions: these For the sake of the discussion and the given drugs are not indicated to clients with examples of drugs, the effects of some drugs in allergy to the drugs, those with particular receptors will be discussed first. hypertension and close angle glaucoma. Alpha 1 receptors when stimulated will cause Caution is used in clients with vasoconstriction, pupillary dilation and closure of cardiovascular disease. urinary bladder sphincter causing urinary retention. Adverse effects: these are related to the When the receptors are blocked? What would be overdose of drugs that may increase the expected effects? sympathetic effects like hypertension, Alpha 2 receptors in the CNS neurons when gastrointestinal depression and stimulated will decrease norepinephrine flow from genitourinary effects like urinary retention the CNS to the SNS therefore decreasing ○ Examples: sympathetic response. Take note that this is the Alpha 1 adrenergic agonist – drug that stimulates adrenergic receptors but Phenylephrine used for treatment decreasing SNS effect because the receptors being of common colds and allergy. stimulated are located in the CNS. This drug causes vasoconstriction Beta 1 receptors in the heart when stimulated will to lessen congestion in the nose increase heart rate. When we use a drug that therefore called decongestants. o blocks the receptor, what is the effect? Alpha 2 adrenergic agonist – Beta 2 is located in the lungs. If we use a drug that Clonidine better known for its stimulates receptors, the effect is bronchodilation. brand name as Catapres acting What is the effect if we block the receptor? on the CNS neurons to decrease norepinephrine flow. This drug is CLASSIFICATIONS OF ADRENERGIC AGONIST DRUGS indicated for treatment of 1. Alpha and Beta adrenergic drugs ( hypertension. Sympathomimetic drugs ) - these drugs stimulate 3. Beta specific adrenergic agonist - these drugs all adrenergic receptors to enhance their effects specifically stimulate the beta receptors and not the Pharmacokinetics: these drugs are alpha receptors. rapidly absorbed, metabolized in the liver Pharmacokinetics: well absorbed and and excreted in the urine. These drugs distributed in the body, metabolized in the may cross the placenta and breastmilk liver and excreted in the urine. The drugs Contraindications and Cautions: Should pass the placenta and breastmilk, use in not be given in client with allergy to these pregnancy and lactation only if benefits drugs and to patients with outweigh the risks BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 11  Contraindications and Cautions: The Pharmacokinetics: these drugs are well drugs are contraindicated in clients with absorbed and distributed, metabolized in allergy to the drugs. Caution is used in the liver and excreted in the urine. clients with cardiovascular disease like Contraindications and Cautions: The hypertension and tachycardia. drugs should not be given to clients with Adverse effects: These are related to the hypotension and urinary incontinence primary effects of drugs which will increase Adverse effects: related to the primary sympathetic effects like hypertension and action of the drug causing vasodilation and tachycardia. hypotension Examples: Examples: Isoproterenol – for treatment of Phentolamine – more specific cardiogenic shock and heart drug hypertension in block in transplanted hearts. pheochromocytoma, that will Salbutamol – for treatment of have less adverse effects. obstructive respiratory disease 3. Alpha 1 selective adrenergic antagonist - these like COPD and bronchial asthma drugs block only the alpha receptors, specific drugs act on the alpha receptors on the blood vessels and ★ Nursing Considerations urinary bladder to cause vasodilation for treatment Avoid sudden withdrawal of the drug of hypertension and bladder emptying for treatment because it may cause rebound of urinary retention. Although some drugs may act hypertension, arrhythmias and flushing in both blood vessels and urinary bladder at the Monitor vital signs especially blood same time pressure and heart rate Pharmacokinetics: drugs are absorbed in Avoid comfort measures including rest and the GIT, metabolized in the liver and environmental control to decrease CNS excreted in the urine. irritation. Contraindications and Cautions: Provide adequate health teaching on the Contraindicated in clients with allergy to name of drug, prescribed dosage, effects the drugs. This may exacerbate and adverse effects to increase patient’s hypotension and urinary incontinence. knowledge and subsequent compliance. Caution is used to clients with cardiovascular disease, gastrointestinal CLASSIFICATIONS OF ADRENERGIC ANTAGONIST and genitourinary conditions DRUGS (SYMPATHOLYTIC DRUGS) Adverse effects: related to the 1. Alpha and Beta adrenergic antagonist - these sympatholytic effect of drugs causing drugs block all adrenergic receptors hypotension and urinary incontinence. Pharmacokinetics: these drugs are well Examples: absorbed and distributed in the body, Prazosin – indicated for metabolized in the liver and excreted in the treatment of hypertension urine and the feces. Terazosin – indicated for Contraindications and Cautions: These treatment of hypertension and drugs should not be given to clients with BPH causing urinary retention allergy to the drugs. To those with Doxazosin – indicated for hypotension and bradycardia. Caution is treatment of hypertension and used in clients with cardiovascular disease BPH causing urinary retention and obstructive lung disorders Alfuzosin indicated for treatment Adverse effects: these mainly on the of BPH effects of the drugs in the lungs like Tamsulosin – indicated for bronchospasm, blood vessels causing treatment of BPH vasodilation and hypotension. 4. Beta adrenergic antagonists - these drugs block Examples both beta 1 and beta 2 receptors, particularly Carvedilol affecting both the heart and the lungs, these drugs Labetalol increase heart rate and bronchoconstriction of the Both examples may be lungs indicated to clients with 5. Beta 1 specific adrenergic antagonist - these severe hypertension drugs block specifically beta 1 receptors in the caused by heart. These drugs are most commonly known as pheochromocytoma beta blockers. These drugs are indicated to clients 2. Alpha adrenergic antagonist - these drugs block with hypertension, dysrhythmias, angina and use to only the alpha receptors, specific drugs act on the support cardiac function in clients with congestive alpha 1 and alpha 2 receptors. heart failure BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 12  Pharmacokinetics: these drugs are Palliative Treatment – control of signs and absorbed in the gastrointestinal tract and symptoms of the disease undergo hepatic metabolism. The Parkinson’s Disease – degenerative disease of presence of food may increase the the nervous system characterized by lack of bioavailability of some beta blockers. neurotransmitter called Dopamine These drugs are known teratogenic in Schizophrenia – most common type of animals as it passes the placenta and psychotic disorder that may cause impairment of breast milk function of an individual in the society Contraindications and Cautions: Seizure – abnormal and excessive impulse Contraindicated in clients with allergy to transmission in the brain the drugs. Caution should be used in Synaptic Transmission – conduction of clients with bradycardia and heart block as impulses across the junction between neurons well on patients with obstructive lung diseases like COPD and bronchial asthma Adverse effects: these are related to the bradycardia and bronchoconstriction effect of the drug. Gastrointestinal effects like nausea and vomiting, genitourinary symptoms may be disturbing to clients as well. Examples Beta adrenergic antagonists or Beta blockers Propranolol Pindolol Beta 1 specific adrenergic antagonists or Beta 1 blockers Metoprolol Atenolol ★ Nursing considerations Avoid sudden withdrawal of the drug because it may cause rebound hypertension, arrhythmias and flushing Monitor vital signs especially blood pressure and heart rate Monitor ECG Avoid comfort measures including rest and environmental control to decrease CNS irritation. Provide adequate health teaching on the name of drug, prescribed dosage, effects and adverse effects to increase patient’s knowledge and subsequent compliance. TERMINOLOGIES Action Potential – this is a rapid change in the membrane potential that explains how impulses are conducted along the nerves Anxiety – feeling of fear, tension or apprehension from known or unknown reasons Depression – affective disorders characterized by extreme sadness, hopelessness and disorganization Mania – characterized by period of extreme over activity and excitement Neurotransmitters – chemicals in the nervous system that help in the transmission of impulses BATCH 2025 TRANSCRIBED BY: AJ & CM | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 13 WEEK 8: AGENTS ACTING ON THE CARDIOVASCULAR SYSTEM NCMA 216 - PHARMACOLOGY 2ND YEAR - BS NURSING (MIDTERMS) Padayon, SN. The heart, a hollow muscle with four chambers comprising A. PATHOPHYSIOLOGY two upper atria and two lower ventricles, pumps oxygenated blood to the body’s cells and also collects waste products from the tissues. The heart’s conduction (or stimulatory) system consists of the SA node, the AV node, the bundle of His, the bundle branches, and the Purkinje fibers generate an impulse, which stimulates the contraction of the heart. The contraction results in a two-step process called the cardiac cycle, namely the diastole (relaxation) and systole (contraction). The cardiovascular system depends on pressure changes to circulate blood to the tissues and back to the heart. B. ANTIHYPERTENSIVE MEDICATIONS: Antihypertensive drugs are organized around a clinical indication—the need to treat a disease—rather than a single receptor type. DISORDERS OF THE HEART: I. HYPERTENSION - excessive high blood pressureIs - Is recognized as a major risk factor for several potentially lethal cardiac conditions, including myocardial infarction and heart failure. This can damage the fragile inner lining of blood vessels and cause a disruption of blood flow to the tissues. It also puts a tremendous strain on the heart muscle, increasing myocardial oxygen consumption and putting the heart muscle at risk. ❖ BP = Heart rate x stroke volume x peripheral a. ACE INHIBITORS (...pril) vascular resistance - Captopril (P) ❖ BP = Cardiac output (heart rate x stroke volume) - Enalapril x peripheral vascular resistance - Lisinopril - Perindopril Pharmacodynamics: ○ blocks angiotensin-converting enzyme (ACE) from converting angiotensin I to angiotensin II, leading to; ○ a decrease in blood pressure