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Does Acute Serotonergic Type‐2 Antagonism Reduce Blood Pressure? Comparative Effects of Single Doses of Ritanserin and Ketanserin in Essential Hypertension

We have studied the acute effects of the serotonergic type-2 (5-HT2) antagonists ketanserin and ritanserin given as single oral doses to patients with essential hypertension. Ketanserin has α1-antagonist properties, whereas ritanserin is largely devoid of α1-receptor binding affinity. Ketanserin (40 mg orally) caused a significant reduction (p < 0.03) of sitting mean arterial pressure over the 8-h period following drug administration by an average of 15.4 ± 3.2 mm Hg (mean ± SEM) as compared to a reduction of 8.5 ± 2.2 following placebo. In contrast, ritanserin had no significant effect on blood pressure compared to placebo; sitting mean arterial pressure was reduced by 9.0 ± 2.6 and 10.8 ± 1.8 mm Hg after administration of 10 and 20 mg, respectively, of ritanserin. There were no significant differences in pulse rate among placebo, ketanserin, or ritanserin phases. Ritanserin caused a reduction in the hostility score (p < 0.05) as measured by the Multiple Affect Adjective Check List; ketanserin had no significant effects. The highly selective 5-HT2 antagonist ritanserin, given in a dose which caused measurable alteration of psychological function tests, had no acute effects on blood pressure. The acute antihypertensive effects of ketanserin are not caused by 5-HT2 antagonism alone, but are likely to be dependent on its α1-antagonistic properties.