Oxprenolol slow-release with cyclopenthiazide-KCl compared with methyldopa in the treatment of essential hypertension. A multicentre general practice trial

Abstract

Two hundred and thirty-eight patients with essential hypertension from 39 general practice centres were treated in a double-blind trial with either oxprenolol 160 mg in a slow-release (SR) formulation with cyclopenthiazide 0,25 mg and potassium chloride 600 mg given once daily, or methyldopa 250 mg 3 times daily. After a 2-week placebo washout period, each patient was treated for 10 weeks. Both treatments significantly reduced blood pressure. Oxprenolol SR plus cyclopenthiazide-KCl was shown to possess significantly superior antihypertensive activity to methyldopa. Pulse rate, as expected, was significantly decreased by the beta-blocker and virtually unaffected by methyldopa. The overall incidence of side-effects was low. The incidence of sleepiness and dry mouth was significantly higher in the methyldopa group, and erythema in the oxprenolol group. The principle of general practitioners conducting multi-centre double-blind trials for research purposes, on drugs which are predominantly given to ambulatory patients, has been established for the first time in South Africa. Virtually no difficulty was encountered in getting patients' consent in the general practice milieu.