Pharmacodynamics and pharmacokinetics of oral pirmenol.

The efficacy, pharmacokinetics, and pharmacodynamics of pirmenol, a class Ia antiarrhythmic agent, were studied in patients with frequent symptomatic premature ventricular complexes (PVCs). Pirmenol was given every 12 hours to eight patients in a dose-ranging protocol, and median PVC suppression of 94% (range 72% to 100%) was achieved. The median effective pirmenol dose was 300 mg/day (range 200 to 500 mg/day), and mean (+/- SD) trough plasma pirmenol concentration at the effective dose was 0.98 +/- 0.29 micrograms/ml. The mean half-life of elimination was 10.5 +/- 2 hours. There was considerable overlap among patients with respect to plasma pirmenol concentration and times at which PVC frequency returned to 25%, 50%, and 75% of baseline during drug washout trials. Altering pirmenol's dose interval (while maintaining a constant daily dose) from 12 to 6 hours did not improve drug efficacy. Pirmenol was given to seven patients for long-term therapy (24 to 44 months). Median PVC suppression at 24 months was 70%. Pirmenol is safe and well tolerated, and it can be administered twice daily for PVC suppression.