Cyproheptadine inhibition of stimulated plasma renin activity

Plasma renin activity (PRA) was stimulated by oral frusemide (60 mg) in 4 normal male subjects. Cyproheptadine (Periactin), a serotonin antagonist, was then administered (2 mg orally four times daily) for 7 days and the PRA response to frusemide re-evaluated in the 4 subjects. A highly significant mean inhibition (P less than 0.01) of frusemide stimulated PRA was demonstrated after cyproheptadine administration. Our results show that serotonin, presumably acting via central pathways, may play a role in renin regulation and that this pathway can be inhibited by cyproheptadine.