The circulatory consequences of concurrent slow-calcium channel (nicardipine) and cardioselective beta blockade (metoprolol) were evaluated in 20 patients with angiographically proven coronary artery disease. The rest and exercise haemodynamic impact of intravenous nicardipine (10 mg) or metoprolol (10 mg) alone was determined by randomly allocating 10 patients to each drug; finally all patients were assessed on combination therapy. The plasma levels of nicardipine (17 +/- 3 to 53 +/- 6 ng ml-1) and metoprolol (36 +/- 5 to 97 +/- 16 ng ml-1) achieved at the time of each study were in the established therapeutic range. At rest nicardipine reduced systemic mean arterial pressure and systemic vascular resistance index; cardiac and stroke volume indices increased without change in pulmonary artery occluded pressure. Metoprolol alone reduced systemic blood pressure, heart rate and cardiac index, and increased systemic vascular resistance index. Combination therapy reduced systemic arterial blood pressure and heart rate with relatively modest effects on cardiac index, systemic vascular resistance index and pulmonary artery occluded pressure. During dynamic exercise nicardipine reduced systemic mean and diastolic arterial pressure and stroke work index without change in other haemodynamic variables. Metoprolol reduced exercise systemic arterial pressures, heart rate and cardiac index, and increased systemic vascular resistance index and pulmonary artery occluded pressure. Combination therapy produced changes similar to those at rest; at peak nicardipine pharmacodynamic activity, the cardiac depressant actions of metoprolol were largely offset by the induced reduction in left ventricular afterload.(ABSTRACT TRUNCATED AT 250 WORDS)