The influence of urinary pH on flecainide excretion and its serum pharmacokinetics.

The effect of urinary pH on flecainide excretion has been evaluated in six healthy subjects after a single oral dose of 300 mg flecainide administered as the acetate salt. The cumulative urinary excretion of unchanged flecainide under acidic conditions (134.0 +/- 16.1 mg; mean +/- s.e. mean) was significantly higher than under alkaline conditions (22.3 +/- 7.6 mg; mean +/- s.e. mean) (P less than 0.01). Under alkaline conditions, tmax (time to reach peak concentration) was reduced (P less than 0.01), while elimination half-life, AUC(0-32) and AUC(0-infinity) were increased (P less than 0.01).