The FDA has added a "black box" warning about the risks of QT prolongation and the potentially fatal torsades de pointes (TdP) ventricular tachycardia to the labeling of droperidol (Inapsine - Akorn), an antiemetic used mostly in anesthesia. The Canadian Health Protection Branch has issued a similar warning. Some anesthesiologists have written to The Medical Letter to express their displeasure with these warnings.

Moricizine (mor i'; siz een) hydrochloride (Ethmozine - Du Pont), a class I antiarrhythmic drug developed in the USSR, was recently approved by the US Food and Drug Administration (FDA) for oral treatment of life-threatening ventricular arrhythmias.

Propafenone (Rythmol - Knoll), a class IC antiarrhythmic drug used in Europe for treatment of various arrhythmias for more than 10 years, was recently marketed in the USA for oral treatment of life-threatening ventricular arrhythmias such as sustained ventricular tachycardia. This restrictive labeling reflects concerns arising from the interim report of the Cardiac Arrhythmia Suppression Trial, in which post-myocardial infarction patients with asymptomatic or mildly symptomatic ventricular arrhythmias treated with the class IC antiarrhythmic drugs encainide (Enkaid) or flecainide...

The drugs of choice for treatment of common cardiac arrhythmias are listed in Tables 1 and 2. Some drugs are recommended for indications that have not been approved by the FDA.

Sotalol (hydrochloride (Betapace -Berlex; Sotacor -Bristol Laboratories of Canada), an antiarrhythmic drug that prolongs repolarization (Class III) and also has beta-adrenergic-blocking activity (Class II), was recently approved by the US Food and Drug Administration (FDA) for oral treatment of life-threatening ventricular arrhythmias.

In recent years, selective destruction of cardiac tissue by radiofrequency energy has become a routine procedure for treatment of some types of cardiac arrhythmias, particularly supraventricular tachycardias (MM Scheinman, Pacing Clin Electrophysiol, 18:1474, 1995).

Flecainide (Tambocor -3M Pharmaceuticals), first introduced in 1985 for treatment of ventricular arrhythmias, was recently approved by the US Food and Drug Administration for oral use to prevent supraventricular arrhythmias. The indications for using flecainide to treat ventricular arrhythmias were limited after a controlled trial found that post-myocardial infarction patients with asymptomatic ventricular arrhythmias who took the drug had twice as high a mortality rate as patients who took placebo (DS Echt et al, N Engl Med, 324:781, 1991).

Some classes of drugs include so many agents that hospital formulary committees, managed care organizations and individual practitioners may find it difficult to choose among them. Fifteen beta-adrenergic receptor antagonists (beta-blockers) are now marketed for systemic use in the USA. One or more have been approved by the FDA for use in hypertension and eight other indications.

Adenosine (Adenocard - Fujisawa), an endogenous purine nucleoside, was recently approved by the US Food and Drug Administration for intravenous treatment of paroxysmal supraventricular tachycardia, including Wolff-Parkinson-White (WPW) syndrome. Adenosine is not approved for and has not been effective in treating atrial flutter, atrial fibrillation, or ventricular tachycardias.

Terfenadine (Seldane - Marion Merrell Dow) and astemizole (Hismanal - Janssen) are nonsedating antihistamines widely used to treat symptoms of allergic rhinitis (Medical Letter, 27:65, 1985; 31:43, 1989). Both are available without a prescription in Canada, and the US Food and Drug Administration is apparently considering terfenadine for over-the-counter availability in the USA.