BRISTOL-MYERS' ENKAID, RIKER's TAMBOCOR WILL BE INDICATED ONLY FOR LIFE-THREATENING ARRHYTHMIAS BASED ON CAST STUDY FINDINGS OF HIGHER MORTALITY

Labeling for Bristol-Myers' Enkaid and Riker's Tambocor will be modified to delete non-life-threatening arrhythmia indications in response to findings from the National Heart, Lung & Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST). After examining interim data on approximately 1,500 patients assigned to Enkaid (encainide) and Tambocor (flecainide), the CAST study data showed "56 deaths or non-fatal cardiac arrests compared to 22 events in the groups being treated with placebo that corresponded to one of those two drugs," Thomas Bigger, Jr., MD, chairman of the CAST steering committee, told an April 25 press conference. "This is a difference that is quite striking . . . your chance of dying or having a non-fatal cardiac arrest is increased about two-and-a-half fold if you were on one of these two drugs compared to the risk if you were on placebo," Bigger commented. The incidence of non-fatal cardiac events and deaths due specifically to arrhythmias was 33 in the drug groups and nine in the placebo groups. The CAST investigators were advised by their review board to discontinue using the drugs in the trial on April 20. Bigger noted that "there was no concern about the third drug" involved in the trial, DuPont's moricizine (Ethmozine), which is not yet approved. The trial is continuing with moricizine and placebo. Both Enkaid and Tambocor have been indicated for "the treatment of documented life-threatening arrhythmias, such as sustained ventricular tachycardia" and "treatment of patients with symptomatic nonsustained ventricular tachycardia and frequent premature ventricular complexes." Enkaid was approved in December 1986; Tambocor was approved in 1985. FDA stressed that the drugs will continue to be recommended for use in treating life-threatening arrhythmias. This indication "is not affected by the NHLBI findings but the [other indication] is no longer appropriate in light of the new findings," the agency said in an April 25 "Talk Paper." Approximately 200,000 people are currently taking either Enkaid or Tambocor, according to Bristol-Myers and Riker. FDA prescription figures show that 586,000 prescriptions were written for the drugs in 1987 and 790,000 in 1988. FDA Office of Drug Evaluation I Director Robert Temple, MD, commented at the briefing that "only a small portion of the current use reflects the indication that we think is still valid." Bristol-Myers and Riker were notified on April 24 of the interim results of the trial. Both Bristol-Myers and Riker sent out "Dear Doctor" letters April 25 informing physicians of the study results and the change in labeling. Riker's letter states: "Tambocor should be used only in patients with life-threatening arrhythmias such as sustained ventricular tachycardia." Riker adds that "decisions on individual patient treatment must be left to you, the treating physician. Physicians are urged to contact their patients on Tambocor if they consider that alternate therapy is indicated." Riker and Bristol-Myers are also providing pharmacists with an informational letter. Bristol-Myers' letter to pharmacists outlines a reimbursement process for unused supplies of Enkaid that are returned by patients who discontinue use. The letter asks that pharmacists "first confirm with the patient's physician that a decision has been made to discontinue Enkaid therapy" and to "provide your customary refund or credit considering initial method of payment." Bristol-Myers noted that it also notified its "field sales force to suspend encainide activities." Both firms are now working with FDA to develop new labeling. Enkaid, Tambocor and Ethmozine are Class 1C anti-arrhythmics. Lilly has an NDA pending for a Class 1C anti-arrhythmic, Decabid (indecainide), for treatment of life-threatening and nonlife-threatening arrhythmias. Lilly said it is examining the CAST study data to evaluate any potential relevance to Decabid. Merck's anti-arrhythmic Tonocard (tocainide) is not viewed as a close chemical relation to the Bristol-Myers and Riker products. CAST, a randomized, double-blind, placebo controlled multicenter study involving 27 centers, was initiated in June 1987 with a planned enrollment of 4,400 patients. The trial was not expected to be completed before 1992. The objective of the trial was to determine whether drugs that reduce asymptomatic ventricular arrhythmias in patients who have had a heart attack will decrease the incidence of sudden cardiac death. Approximately 1,500 patients with asymptomatic, non-life-threatening arrhythmias were randomized to receive the three drugs or placebo. The study findings will be published in a major medical journal, NHLBI said.