BIOTRANSFORMATION AND ELIMINATION OF C-14 FLECAINIDE ACETATE IN HUMANS

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  • 1 January 1984
    • journal article
    • research article
    • Vol. 12  (4) , 414-420
Abstract
The metabolism of 14C-flecainide acetate, a new antiarrhythmic, was investigated in 4 healthy human subjects, after a single, 200-mg oral dose. The cumulative recovery of radioactivity ranged from 81-90% (mean, 86%) in urine and from 4-6% (mean, 5%) in feces; thus, flecainide does not appear to undergo extensive biliary excretion, unless reabsorption occurs after biliary elimination. The cumulative excretion in urine of unchanged flecainide ranged from 35-50% (mean, 42%) of the dose and was essentially complete by 72 h postdose. Peak plasma levels of radioactivity (524-848 ng eq/ml) and of unchanged flecainide (214-281 ng/ml) were attained at 2-3 h postdose. The average half-life for the disappearance of unchanged flecainide from plasma was about 16 h, disappearance of total metabolites from plasma was only slightly slower. Radiomonitored TLC analysis showed that urine contained 2 major metabolites and 2 or 3 minor ones; both major metabolites were extensively conjugated. By TLC, NMR and mass spectral comparisons to reference compounds, the 2 major urinary metabolites were m-O-dealkylated flecainide and the m-O-dealkylated lactam of flecainide. Most of the radioactivity in urine was accounted for by flecainide and the 2 major metabolites.

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