A reversed-phase HPLC method for determination of isotetrandrine (ITD) in biological specimens was developed. The mobile phase composed of 0.2% (w/v) SDS, 47% acetonitrile and 53% distilled water (pH 2), at a flow rate of 1.5 ml/min with determination wavelength of 230 nm. The drug concentration-time curves of ITD in rats after iv of 12.5, 25 and 50 mg/kg were shown to fit a two-compartment open model with half-lives of 67.1 +/- 6.22 68.0 +/- 2.57 and 97.6 +/- 14.6 min, respectively. At doses of 12.5 and 25 mg/kg, the elimination of the drug from plasma was found to be in accord with linear kinetics, but when the dosage was 50 mg/kg, a non-linear kinetics was observed. Following ig ITD 100 and 250 mg/kg, the plasma concentration-time curves exhibited two marked peaks. Half-lives of elimination after ig doses was much longer than after iv administration, with mean values of 9.35 +/- 3.24 h (100 mg/kg) and 9.01 +/- 3.02 h (250 mg/kg). Distribution of the drug in rats was extensive, highest level of the drug was found in the lung and lowest in plasma after iv administration. Following ig administration, highest level of the drug was found in the liver and lowest in plasma.