Hydralazine in arterial hypertension. Randomized double-blind comparison of conventional/Slow-Release formulation and of b.i.d./q.i.d. dosage regimens.

Blood pressure (BP) control and tolerability of three two-week dosage regimens of hydralazine--conventional hydralazine q.i.d., conventional hydralazine b.i.d. and slow-release hydralazine b.i.d--were compared in a double-blind, randomized, cross-over trial in 20 out-patients with arterial hypertension controlled with hydralazine in combination with other antihypertensive drugs. The efficacy of the treatments was assessed during the last two days of each treatment period by determination of BP and pulse rate every hour between 8 a.m. and 6 p.m. No statistically significant differences in BP and pulse rate were found between the three treatment regimens, either in the variation during the day or in the mean value for the day. There was a tendency to lowest BPs on conventional hydralizine q.i.d. and to highest on conventional hydralazine b.i.d. Mean differences in supine BP between conventional hydralazine b.i.d. and slow-release hydralazine b.i.d. were 3.2 systolic and 0.5 mmHg diastolic. In this short-term study, mean values with 95% confidence limits indicate that conventional hydralazine in a q.i.d. dosage can be replaced by the same preparation or slow-release formulation in a b.i.d. dosage. Acetylator phenotype was determined and had no significant influence on the results, although there was a tendency to more widespread variability in systolic pressure and to a lower pulse rate in fast acetylators. Unwanted effects were few and did not differ obviously between the treatments. Whether the frequency of late toxicity of hydralazine is lower with slow-release formulation remains to be evaluated in long-term studies.