Introductory Clinical Pharmacology Chapter 39 Antiarrhythmic Drugs

Antiarrhythmic: Actions Antiarrhythmic drugs are classified according to their effects on the action potential of cardiac cells and their presumed mechanism of action Class I: Have a membrane-stabilizing or anesthetic effect on the cells of the myocardium Class IA: Depress phase 0; prolong the action potential Class IB: Slightly depress phase 0; shorten the action potential duration

Antiarrhythmic: Actions (cont’d) Class IC: Marked depression of phase 0; slight effect repolarization; profound slowing of conduction Class II: Depression of depolarization phase 4; blocking beta-adrenergic receptors of the heart and kidney Class III: Prolongation of repolarization (phase 3) Class IV: Depressing depolarization (phase 4); lightening phase 1 and 2 of repolarization

Antiarrhythmic: Uses and Adverse Reactions Used to treat: Premature ventricular contractions; ventricular tachycardia; paroxysmal atrial tachycardia; other atrial arrhythmias such as atrial fibrillation or flutter; tachycardia when rapid but short-term control of ventricular rate is desirable CNS reactions: Light-headedness; weakness; somnolence Cardiovascular reactions: Hypotension; arrhythmias; bradycardia Other: Urinary retention; local inflammation

Antiarrhythmic: Contraindications Contraindicated: Patients with known hypersensitivity to the drug; during pregnancy and lactation; patients with second- or third-degree AV block (if the patient has no artificial pacemaker); severe congestive heart failure (CHF); aortic stenosis; hypotension; and cardiogenic shock Antiarrhythmic drug amiodarone used during pregnancy only if the potential benefits outweigh the potential hazards to the fetus Quinidine and procainamide are contraindicated in patients with myasthenia gravis

Antiarrhythmic: Precautions Used cautiously in patients with renal or hepatic disease, electrolyte disturbances, CHF (quinidine, flecainide, procainamide and disopyramide), and renal impairment Disopyramide is used cautiously in patients with myasthenia gravis, urinary retention, glaucoma, and in men with prostate enlargement

Nursing Process: Assessment Preadministration assessment Take and record blood pressure, apical and radial pulses, and respiratory rate; assess the patient’s general condition, including observations such as skin color (pale, cyanotic, flushed), orientation, level of consciousness, and the patient’s general status (such as appears acutely ill or appears somewhat ill); recording any symptoms (subjective data) described by the patient Review the test results before the first dose is given

Nursing Process: Assessment Ongoing assessment Take the patient’s blood pressure, apical and radial pulses, and respiratory rate at periodic intervals Observe the patient for a response to drug therapy, signs of CHF, the development of a new cardiac arrhythmia, or worsening of the arrhythmia being treated Report to the primary care provider any abnormalities or significant interval changes of the ECG

Nursing Process: Planning The expected outcomes for the patient depend on the reason for administration of the antiarrhythmic drug, but may include: Optimal therapeutic response to drug therapy Supporting patient’s needs related to management of adverse reactions Understanding of and complying with prescribed drug regimen

Nursing Process: Implementation Promoting an optimal response to therapy Administering quinidine: Monitor serum quinidine levels during administration of the drug; normal therapeutic levels range between 2 and 6 mg/mL Administering procainamide If given IV, maintain continuous and close cardiac monitoring; keep patient supine during IV administration to minimize hypotension

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering procainamide (cont’d) When drug given orally, instruct the patient not to chew the capsule or tablet but to swallow it whole; If GI upset occurs, administer the drug with or immediately after meals Administering disopyramide: Monitor cardiac rhythm and blood pressure during therapy

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering lidocaine Constant cardiac monitoring is essential when this drug is administered IV Observe the patient closely for signs of respiratory depression, bradycardia, change in mental status, respiratory arrest, convulsions, and hypotension

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering lidocaine (cont’d) An oropharyngeal airway and suction equipment are kept at the bedside in case convulsions should occur; life support equipment and vasopressors are also readily available in case of adverse reaction

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering mexiletine: Dosage of mexiletine must be individualized; therefore, monitor vital signs at frequent intervals during initial therapy; report any changes in the pulse rate or rhythm to the primary health care provider; adverse effects related to the CNS or GI tract may occur during initial therapy and must be reported to the primary health care provider

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering flecainide and propafenone When administering flecainide, carefully monitor the patient for cardiac arrhythmias; life support equipment, including pacemaker, should be kept on standby during administration; observe the patient for a response to drug therapy, signs of CHF, the development of a new cardiac arrhythmia, or worsening of the arrhythmia being treated

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering flecainide and propafenone (cont’d) Propafenone is administered orally every 8 hours; any previously given antiarrhythmic drug should be discontinued before propafenone therapy is started; patient must be monitored carefully; periodic ECG monitoring is usually ordered to evaluate the effects of the drug on cardiac conduction

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering propranolol: Cardiac monitoring is recommended when propranolol is given IV because severe bradycardia and hypotension may occur; obtain written instructions from the primary health care provider for propranolol administration; monitor the ECG frequently for cardiac arrhythmias; monitor the blood pressure and pulse frequently during the dosage adjustment period and periodically throughout therapy

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering bretylium: Used in the emergency treatment of life-threatening ventricular arrhythmias; administer this drug IM or IV and use continuous cardiac monitoring; monitor cardiac rhythm and blood pressure continuously during administration

Nursing Process: Implementation Promoting an optimal response to therapy (cont’d) Administering verapamil: Monitor the patient’s blood pressure and cardiac rhythm carefully while the drug is being titrated (dosage increased or decreased based on an established criteria by the primary care provider); notify the primary health care provider if bradycardia or hypotension occurs

Nursing Process: Implementation Monitoring and managing patient needs Nausea: Advise the patient that eating small meals frequently may be better tolerated than three full meals daily; tell the patient to avoid lying flat for approximately 2 hours after meals; administer the drug with meals to decrease GI effects Urinary retention: Monitor the urinary output closely, especially during the initial period of therapy; if the patient’s intake is sufficient but the output is low, the lower abdomen is palpated for bladder distention

Nursing Process: Implementation Monitoring and managing patient needs (cont’d) Impaired oral mucous membrane: Provide an adequate amount of fluid and instruct the patient to take frequent sips of water to relieve this problem; sucking on hard candy (preferably sugarless candy) will help to keep mouth moist Risk for injury: Assist patients who are not on complete bed rest to ambulate until these symptoms subside; postural hypotension also may occur during the first few weeks of disopyramide therapy, patient is advised to make position changes slowly

Nursing Process: Implementation Monitoring and managing patient needs (cont’d) Risk for infection: Report any signs of agranulocytosis such as fever, chills, sore throat, or unusual bleeding or bruising; complete blood count is usually ordered every 2 to 3 weeks during the first 3 months of therapy Potential complication: Proarrhythmic effects may occur, such as ventricular tachycardia or ventricular fibrillation

Nursing Process: Implementation Monitoring and managing patient needs (cont’d) Potential complication: quinidine toxicity; monitor the patient for the most common adverse reactions associated with quinidine (nausea, vomiting, abdominal pain, diarrhea, or anorexia); report any quinidine levels greater than 6 μg/mL and the occurrence of any of the following signs or symptoms of cinchonism: ringing in the ears (tinnitus), hearing loss, headache, nausea, dizziness, vertigo, and light-headedness

Nursing Process: Implementation Educating the patient and family Discuss the adverse drug effects that may occur with the patient and family To ensure compliance with the prescribed drug regimen, emphasize the importance of taking these drugs exactly as prescribed Teach the patient or a family member how to take the pulse rate and report any changes in the pulse rate or rhythm to the primary health care provider

Nursing Process: Evaluation The therapeutic response is achieved and the arrhythmia is controlled Adverse reactions are identified, reported to the primary health care provider, and managed successfully with appropriate nursing interventions The patient reports no nausea and urinary retention; oral mucous membranes are intact and moist; no symptoms of infection experienced; no evidence of injury seen

Nursing Process: Evaluation (cont’d) The patient and family demonstrate an understanding of the drug regimen The patient verbalizes the importance of continued follow-up care The patient verbalizes the importance of complying with the prescribed treatment regimen The patient complies with the prescribed drug regimen

End of Presentation