Antiarrhythmic agents drugs

Mason DT, DeMaria AN, Amsterdam EA, Zelis R, Massumi RA. Antiarrhythmic agents. Drugs 1973 5(4) 261-317. 

Trujillo TC, Nolan PE. Antiarrhythmic agents drug interactions of clinical significance. Drug Saf 2000 23(6) 509-32. 

ICDs have been found to be significantly more effective than antiarrhythmic agents such as amiodarone or sotalol for reducing the risk of sudden cardiac death 45,46 therefore, ICDs are preferred therapy.44 However, many patients with ICDs receive concurrent antiarrhythmic drug therapy to reduce the frequency with which patients experience the discomfort of shocks and to prolong battery life of the devices. Combined pharmacotherapy with amiodarone and a 3-blocker is more effective than monotherapy with sotalol or (i-blockers for reduction in the frequency of ICD shocks.47... 

Proarrhythmia refers to development of a significant new arrhythmia (such as VT, ventricular fibrillation [VF], or TdP) or worsening of an existing arrhythmia. Proarrhythmia results from the same mechanisms that cause other arrhythmias or from an alteration in the underlying substrate due to the antiarrhythmic agent. TdP is a rapid form of polymorphic VT associated with evidence of delayed ventricular repolarization due to blockade of potassium conductance. TdP may be hereditary or acquired. Acquired forms are associated with many clinical conditions and drugs, especially type la and type III IKr blockers. 

AF often recurs after initial cardioversion because most patients have irreversible underlying heart or lung disease. A metaanalysis confirmed that quinidine maintained sinus rhythm better than placebo however, 50% of patients had recurrent AF within 1 year, and more importantly, quinidine increased mortality, presumably due in part to proarrhythmia. Type Ic (e.g., flecainide, propafenone) and type III (e.g., amiodarone, sotalol, dofetilide) antiarrhythmic agents may be alternatives to quinidine however, these agents are also associated with proarrhythmia. Consequently, chronic antiarrhythmic drugs should be reserved for patients with recurrent paroxysmal AF associated with intolerable symptoms during episodes of AF. 

Drug related Use of antiarrhythmic agents (class I or class III)... 

Is the drug likely to he co-prescribed with a drug of narrow therapeutic index For example, a drug for angina, cardiac failure or an antiarrhythmic agent is likely to be co-prescribed with warfarin. If there is any evidence of enzyme induction or inhibition, a clinical study with warfarin may be required. 

In addition to being used as antianginal and antiarrhythmic agents, calcium channel blockers are used to treat weak and moderate hypertension. These drugs prevent calcium ions from entering into the smooth muscle cells of peripheral vessels, and they cause relaxation of peripheral vessels, which leads to lowering of arterial blood pressure. In clinically used doses, calcium channel blockers relax smooth musculature of arteries and have little effect on veins. In doses that relax smooth musculature, calcium channel blockers have relatively little effect on cardiac contractility. 

Proarrhythmic effects Antiarrhythmic agents may cause new or worsened arrhythmias. It is essential that each patient be evaluated electrocardiographically and clinically prior to and during therapy to determine whether the response to the drug supports continued treatment. ... 

The applicability of these results to other populations (eg, those without recent Mis) is uncertain. Considering the known proarrhythmic properties of procainamide and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, the use of procainamide and other antiarrhythmic agents should be reserved for patients with life-threatening ventricular arrhythmias. 

Concurrent antiarrhythmic agents Concurrent antiarrhythmic agents may produce enhanced prolongation of conduction or depression of contractility and hypotension, especially in patients with cardiac decompensation. Reserve concurrent use of procainamide with other Class lA antiarrhythmic agents (eg, quinidine, disopyramide) for patients with serious arrhythmias unresponsive to a single drug and use only if close observation is possible. 

Dolasetron Hypersensitivity to the drug or components of the product markedly prolonged QTc or atrioventricular block II to III patients receiving class I or III antiarrhythmic agents. 

Drugs that may interact with nalidixic acid include theophylline, caffeine, oral anticoagulants, bacteriostatic agents, probenecid, antacids (containing magnesium, aluminum, and calcium), sucralfate, iron salts, multivitamins containing zinc, didanosine, antiarrhythmic agents, and melphalan. 

Drugs that may be affected by fluoroquinolones include caffeine, cyclosporine, digoxin, antiarrhythmic agents, bepridil, erythromycin, phenothiazine, tricyclic antidepressants, procainamide, anticoagulants, and theophylline. 

Hi-receptor but also at muscarinic cholinoceptors, serotonin receptors, and adrenoceptors. This explains the atropine-like side effects of those drugs. The cationic amphophilic structure of these substances resemble that of antiarrhythmic agents which might explain the arrhythmogenic properties seen with some of these Hi-antagonists. 

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