Modification of antihypertensive effect of beta-adrenoceptor-blocking agents by inhibition of endogenous prostaglandin synthesis.

The effect of indomethacin-induced inhibition of endogenous prostaglandin synthesis on the antihypertensive activity of pindolol (15 mg daily) and propranolol (80--160 mg daily) was studied in 7 hypertensive patients. In four test phases of 10 days each, patients received beta-blocker alone, placebo, beta-blocker plus indomethacin (100 mg daily), and beta-blocker alone. Mean supine diastolic blood-pressure rose from 82 +/- 2 mm Hg in the first beta-blocker phase to 98 +/- 3 mm Hg in the placebo phase, remained elevated (96 +/- 3 mm Hg) in the beta-blocker-plus-indomethacin phase, and fell to 83 +/- 3 mm Hg in the last beta-blocker phase. Diastolic blood-pressure values obtained in the beta-blocker-plus-indomethacin phase were not significantly different from those obtained in the placebo phase but were significantly different from the values measured in both beta-blocker phases (P less than 0-01). The changes in systolic blood-pressure and pulse-rate were not significant. These preliminary results suggest that the antihypertensive effect of these two beta-blockers in some hypertensive patients may be related to the endogenous prostaglandin system.