In two groups of female patients with metastatic breast cancer who had all been pretreated with doxorubicin (350 mg/m2), acute cardiac effects following i.v. doxorubicin bolus injection (60 mg/m2) were recorded on the basis of systolic time intervals (STI). In six patients who received doxorubicin only the ratio between the heart-beat-corrected preejection period and left ventricular ejection time (PEPI:LVETI) as well as the PEP index were found to be significantly increased with a peak at 6 h following drug infusion (P less than 0.001). Another six patients received an identical chemotherapeutic regimen and, in addition, a combination of tocopherol (200 mg i.m. 6 h before treatment) and nifedipine (60 mg p.o. daily from 2 days before doxorubicin infusion). In the pretreatment group, the PEPI:LVETI ration and PEP index remained unchanged during the posttreatment period. Pharmacokinetic analysis of drug concentrations in the plasma revealed a significantly accelerated distribution and elimination of doxorubicin after combined tocopherol and nifedipine pretreatment, although no statistically significant differences could be found in calculated drug levels in the peripheral compartment between both treatment groups. Our results indicate that acute cardiac reactions reflected by changes in STI values can be prevented by combined tocopherol and nifedipine pretreatment.