Heart-rhythm drugs found risky for many.

Heart-rhythm drugs found risky for many

Noting that two drugs under evaluation increased patients' chances of sudden cardiac death, federal officials this week halted a major portion of a large, multicenter clinical trial designed to evaluate the long-term effectiveness of drugs that suppress abnormal heart rhythms. early results of the National Institutes of Health-sponsored study have prompted the FDA to narrow its recommendations for use of the two drugs, both of which have been on the market for more than two years.

Study patients taking encainide (marketed as Enkaid by Bristol Laboratories in Evansville, Ind.) and flecainide (marketed as Tambocor by 3M Riker in St. Paul, Minn.) showed a two- to three-fold greater risk of cardiac arrest or death compared with patients taking placebo after an average treatment period of 10 months. A third drug in the trial, moricizine, so far shows no significant adverse or beneficial trends in comparison with placebo and will continue under investigation. Moricizine has yet to gain FDA approval and is not available for general use.

Begun in June 1987 and designed to run until 1992, the Cardiac Arrhythmia Suppression Trial sought to compare each of the three drugs to placebo in a total of 4,400 patients who had a heart attack and developed arrhythmias within two years before enrollment in the study. Earlier tests had confirmed that both of the FDA-approved drugs suppress cardiac arrhythmias. But this trial was the first to examine death rates in patients taking the drugs.

Early review of the data by an independent safety monitoring board revealed that 56 of 730 patients given encainide or flecainide had died from some cause or suffered a heart attack, compared with 22 of 730 patients given placebo. specifically, 33 taking one of the two drugs experienced sudden cardiac death or a nonfatal heart attack, compared with 9 in the placebo group.

Company representatives estimate that about 200,000 U.S. patients with various degrees of cardiac arrhythmias currently take one of the two drugs with drawn from the study. NIH and FDA officials emphasize that these patients should not stop taking the drugs without consulting a physician. In a "Dear Doctor" letter the FDA is distributing nationwide, health professionals will be informed that the two drugs are to be reserved almost entirely for "immediately life-threatening arrhythmias" and only rarely used for less threatening arrhythmias.

Other FDA-approved anti-arrhythmics exist but are more toxic than encainide and flecainide and have not been tested for their effects on mortality. Both of the two newer drugs act on heart-muscle cell membrances, slowing electrical conduction in the heart and normalizing extremely rapid or otherwise untimely contractions that can lead to cardiac arrest.

More than 1 million people in the United States show some symptoms of cardiac arrhythmia.