Azimilide is a new class III antiarrhythmic drug that blocks K+ channels. To determine the effects of age and gender on azimilide pharmacokinetics, a single 150-mg oral dose was administered to 66 healthy volunteers in a 3 x 2 factorial design (age groups of 18-40, 41-64, and > or = 65 years). Blood and urine were analyzed for azimilide and metabolites. The single dose was well-tolerated. Azimilide was 94% plasma protein-bound, and binding was not affected by age or gender. Age does not affect azimilide pharmacokinetics. The renal clearance of azimilide was significantly higher in women than in men (19%), but oral clearance did not differ between genders. Although the maximum azimilide concentration (Cmax) was 27% higher in women, time to maximum concentration or area under the azimilide concentration-time curve were not different from those for men. Body weight-adjusted Cmax did not differ between genders. Dosing adjustments based on either age or gender are not required.