PHARMACOKINETIC AND ELECTROCARDIOGRAPHIC STUDY OF ORAL VERAPAMIL SUSTAINED RELEASE TABLET IN 10 CHINESE VOLUNTEERS

Both verapamil pharmacokinetics and electrocardio graphic changes in 10 Chinese volunteers were studied after po 240 mg of verapamil sustained release tablet. A one compartment model with zero order absorption gave a better fitting to concentration-time data with values of r²>0.96. The main pharmacokinetic parameters obtained were: T_max, 5.9±1.6 h; C_max, 118.9±37.2 μg·5L^-1 ; T₁, 5.4±1.5 h; k₀, 30.5±17.5 μg·5L^-1 5h -1 ; T_1/2, 10.8 ±4.9 h; MRT, 15.4±3.2 h and AUC. 1.96±0.82 mg·5h·5L^-1 . There were significant prolongations of PR intervals after dose. Relationships between PR interval changes and plasma concentrations of verapamil were better fitted to sigmoidal model, with r²>0.98. The corresponding pharmacodynamic parameters were estimated. EC₅₀ , 64.6±16.9 μg·5L^-1 , E_max, 54±11 ms and s, 1.68±0.66.