Acute and long-term hemodynamic effects of tiapamil at rest and during exercise in essential hypertension

The first dose and long-term hemodynamic responses to tiapamil--an aralkylamine calcium-channel blocker--were studied both at rest and during exercise in 18 male patients (mean age, 45 years) with essential hypertension (EH). Blood pressure (BP) was measured intra-arterially, cardiac output (CO) was measured by dye dilution and heart rate (HR) was measured by electrocardiogram. One hour after the first oral dose of 600 mg tiapamil, mean arterial pressure (MAP) fell 14%. Total peripheral resistance (TPR) fell 21%, while HR and CO increased 7% and 11%, respectively. Thereafter the effects leveled off. After 11 months of chronic tiapamil therapy (mean dose 980 mg per day), MAP was reduced 11% at rest sitting. The reduction in BP was associated with a modest reduction in TPR. Similar responses were seen at rest supine and during 100-W bicycle exercise. A small reduction was seen in HR while CO was preserved. In conclusion, tiapamil exerts a moderate antihypertensive effect, both at rest and during exercise, through reduction of TPR without a fall in heart pump function. The long-term hemodynamic changes are rather similar to those of verapamil.