Antihypertensive action and serotonin-induced platelet aggregation during long-term ketanserin treatment in hypertensive patients.

Ketanserin (3 X 40 mg daily) was administered during 6 weeks in 14 patients with mild to moderate essential hypertension using a double-blind, placebo-controlled, crossover design. Ketanserin decreased (p less than 0.01) the recumbent blood pressure from 159/104 to 153/97 mm Hg and the recumbent heart rate from 75 to 72 beats/min. Platelet aggregation induced by 5-hydroxytryptamine (5-HT), whether or not amplified by threshold doses of collagen, was not inhibited; however, it was reduced in 10 normal volunteers after a single oral dose of 40 mg ketanserin. The results suggest that long-term treatment with ketanserin reduces blood pressure; whereas 5-HT receptor inhibition could not be demonstrated when assessed by platelet aggregation.