Plasma flecainide concentrations following acute myocardial infarction.

Plasma flecainide concentrations were measured in 10 patients with acute myocardial infarction. Following an oral loading dose of 300 mg plasma concentrations were highly variable and unpredictable. Subsequently, doses of 150 mg twice daily produced mean plasma flecainide concentrations consistently above 400 micrograms/1 within 48 hours. Oral flecainide is, therefore, subject to the same problems of varying oral bioavailability as other antiarrhythmic drugs tested following acute myocardial infarction and, initially, an intravenous regime remains preferable. Mild pulmonary oedema occurred in six patients and, although it responded to one dose of frusemide and did not recur, flecainide must be used with caution when significant left ventricular dysfunction is suspected.