Clinical evaluation of the vasodilator MDL-899 in patients with essential hypertension.

In this study of 10 patients with essential hypertension inadequately controlled by standard beta-blocker-diuretic combination therapy, the addition of 5 mg of MDL-899, a peripheral arteriolar vasodilator, resulted in significant reductions in blood pressure, both supine and standing, which was maximal 4-8 h after dosing, with no additional orthostatic component. There were associated small rises in heart rate but no evidence of significant activation of the sympathetic or renin-angiotensin systems. Six patients continued for 4 weeks receiving MDL-899 twice daily with significant improvement in their blood pressure control--from a mean of 182/95 to 146/77 mm Hg (supine) and from 161/93 to 138/79 mm Hg (erect). These six patients experienced no significant side effects, but four patients were unable to proceed with the study as a result of adverse effects, particularly headache, following the first few doses. It seems likely that these side effects are dose related. In a combined drug regimen, MDL-899 is an effective vasodilator drug that significantly improved the blood pressure control of patients with essential hypertension.