Abstract: On measuring the percentage of QTc interval prolongation, the pharmacokineticand pharmacodynamic profiles of iv matrine or oxymatrine in rabbits were analyzed by combined phar-macokinetic and pharmacodynamic model. The plasma concentration-time profiles of the two drugscan be described by a two-compartment open model, and the relationship between effect and effectcompartment concentration of both drugs can be represented by the sigmoid E_max model. Marked differ-ences in pharmacokinetic and pharmacodynanic parameters between the two drugs were found, buttheir pharmacokinetic and pharmacodynamic properties were dose-independent in the dose ranges usedin the experiment.