Hydralazine and Oxprenolol in the Treatment of Hypertension and the Effect of these Drugs on Plasma Renin Activity

The effect of a vasodilator (hydralazine), a beta-blocker (oxprenolol) and also their combination, on essential arterial hypertension and plasma renin activity (PRA), was studied. Eighteen patients with mild hypertension (WHO I or II) were treated for 4 weeks with oxprenolol, hydralazine and their combination, with 4-week placebo periods between the active treatment periods. Oxprenolol and hydralazine lowered the blood pressure to a similar degree and their combination accentuated this effect. PRA decreased significantly on both the oxprenolol and the combination therapy, but increased during the following placebo and hydralazine periods to a level slightly higher than the initial level. Another group of eleven patients were treated with oxprenolol for 20 weeks. Blood pressure decreased almost to a normotensive level during the first 4 weeks of treatment and a little lower during the following 4 weeks. It remained at this level until the end of the trial. PRA decreased significantly during the first 4 weeks on oxprenolol and remained low during the whole 20-week treatment period. No correlation was found between the change in blood pressure caused by oxprenolol treatment and the initial placebo value of PRA, or, the change in PRA on oxprenolol treatment. These results support the view that the level of PRA has no significance when an antihypertensive treatment is being selected, e.g. beta-blockers.