Instead of preventing cardiac arrest, encainide
and flecainide caused cardiac arrest.
Recently, the Cardiac Arrhythmia Suppression Trial showed that the Class Ic drugs flecainide and encainide
increased mortality by two and a half times compared with placebo in patients who were enrolled 6 days to 2 years after myocardial infarction and had six or more ventricular ectopics per hour, with no sustained ventricular tachycardia[6, 7].
Drugs which could be affected by poor metabolism include metoprolol, a 13-blocker, and recently Encainide
, scheme 5, a potent drug which suppresses irregular heart beats and which has been examined in patients by Laganiere in collaboration with the Ottawa Heart Institute and other North American centres.
Study patients taking encainide
(marketed as Enkaid by Bristol Laboratories in Evansville, Ind.
7%; 56/730) was seen in patients treated with encainide
or flecainide (Class 1C antiarrhythmics) compared with that seen in patients assigned to placebo (3.
9] The Cardiac Arrhythmia Suppression Trial (CAST) Investigators, "Preliminary report: effect of encainide
and flecainide on mortality in a randomized trial of arrhythmia suppression after myocardial infarction," The New England Journal of Medicine, vol.
12) Similarly, encainide
and flecainide reduce the incidence of arrhythmias after acute myocardial infarction, but they also increase mortality.
Increased risk of death and cardiac arrest from encainide
and flecainide in patients after non-Q-wave acute myocardial infarction in the Cardiac Arrhythmia Suppression Trial.
Mortality in patients treated with flecainide and encainide
for supraventricular arrhythmias.
was provided by Bristol-Myers, Princeton, NJ.
The widespread use of encainide
and flecainide before POEMs were available led to more than 50,000 premature deaths, more than all the Americans killed during the Vietnam War.
For example, although encainide
suppresses ventricular arrhythmias, it increases mortality; gemfibrozil lowers cholesterol, but it does not reduce cardiovascular or all-cause mortality; and while calcium-channel blockers reduce blood pressure, they increase the risk of acute myocardial infarction when compared with angiotensin-converting enzyme inhibitors in hypertensive patients with diabetes.
Antiarrhythmics Amiodarone Encainide
Flecainide Mexilitine N-propylamaline Propafenone Sparteine Antidepressants Imipramine Desipramine Amitriptyline Nortriptyline Clomipramine Beta-blockers Propranolol Timolol Bufuralol Metoprolol Neuroleptics Perphenazine Thioridazine Miscellaneous Codeine Debrisoquine 4-OH amphetamine Indoramin Phenformin Table 5.
Still, SSRIs should not be administered concomitantly to patients being treated with type IC antiarrythmics (eg, encainide
, flecainide, and propafenone) because SSRIs block the metabolism of these antiarrhythmics (via inhibition of cytochrome P450 2D6), resulting in high concentrations and, possibly, treatment-emergent arrhythmias.
is a class IC antiarrhythmic agent that is used in the treatment of life-threatening ventricular arrhythmias.