Pharmacokinetics and central haemodynamic effects of doxorubicin and 4'epi-doxorubicin in the pig.

The relationship between the cardiotoxicity and the haemodynamics/pharmacokinetics of clinical concentrations of doxorubicin and 4'epi-doxorubicin was studied. Twelve pigs were randomized to receive i.v. infusions of either drug of 50 mg/m2 over 3.0 min. Aortic, pulmonary arterial, coronary sinus and central venous plasma concentrations of the agents were determined until 180 min after the infusion. The V5 ECG, left ventricular dP/dT, aortic, pulmonary arterial and right atrial pressures were recorded continuously, cardiac output and coronary sinus blood flow were recorded intermittently. No haemodynamic changes were recorded after administration of either drug. Pharmacokinetic data indicated myocardial extraction, followed by myocardial release of both drugs. This release was higher after administration of 4'epi-doxorubicin than after doxorubicin, within the range 2-4 min and 20-40 min after the infusion. The tendency of greater myocardial release of 4'epi-doxorubicin may explain its lower cardiotoxicity.