Absorption kinetics of procainamide in humans.

Plasma procainamide concentrations following the administration of 500 mg of procainamide hydrochloride via intravenous infusion, conventional capsules, and sustained-release tablets were compared in 11 healthy male volunteers. Two-compartment open modeling of the plasma levels from the intravenous infusion experiments yielded mean Kel, k12, and k21 values of 0.0162, 0.0542, and 0.0233 min-1, respectively. The bioavailability of the oral preparations (versus intravenous) averaged 83% for the capsule and 79% for the sustained-release tablet. Calculations using a previously reported method suggested that absorption was a first-order process with mean ka's of 0.0336 and 0.0039 min-1 for the capsule and sustained-release tablet, respectively. The sustained-release formulation exhibited delayed release and adequate bioavailability.