Comparative study of oxdralazine and dihydralazine in essential hypertension

Thirty-one patients with moderate and severe essential hypertension completed a comparative study of oxdralazine and dihydralazine. Treatments were administered for a 6-month period. The therapeutic regimen also included diuretic and a beta-blocking agent given at a constant daily dose. After a 4-week run-in period on diuretic plus beta blocker, which caused a mean blood pressure reduction of 17/7 mmHg, the administration of the vasodilators produced a further, more marked decrease of pressure values. After 1-month treatment mean blood pressure reductions were 26/18 mmHg on oxdralazine and 16/11 mmHg on dihydralazine. After 6 months, 10/15 patients on oxdralazine and 7/16 patients on dihydralazine had achieved a stabile diastolic pressure below 95 mmHg. These results were confirmed by an additional phase of the study, in which 21 patients had the vasodilator cross-over and were observed for a second 6-mont period. Oxdralazine and dihydralazine therapy were well tolerated: only a few patients complained of side effects that were of mild intensity and never required any change in treatment. At the first visit after the cross-over, those patients changing from oxdralazine to dihydralazine complained of side effects with a higher frequency than the patients changing from dihydralazine to oxdralazine. In one patient from the former group it was necessary to stop dihydralazine treatment.