[Antihypertensive vasodilators].

Abstract

Antihypertensive vasodilators share the capability of producing vasodilation of arterioles. In addition, two of them, i.e. nitroprussiate and prazosine, also produce vasodilation of veinulae. Both of these agents cause a simultaneous decrease in pre-load and post-load, and may be used in heart failure. The effectiveness of vasodilators is offset by regulatory cardiac and/or renal mechanisms, and the association with a sympatholytic agent and/or a diuretic is generally needed. Consequently, vasodilators are usually the third step in the course of managing a hypertensive patient. Association with a betablocking agent is especially necessary in patients with coronary insufficiency, in order to prevent an increase in myocardial oxygen requirements and worsening of angina pectoris. Vasodilators are active within a fairly wide dosage range, making individualized dosages requisite. In treating hypertension by the oral route, daily doses above 200 mg for dihydralazine, 60 mg for minoxidil and 10 mg for prazosine are only exceptionnaly useful. In emergency treatment of hypertension, diazoxide and nitroprussiate can be used only in patients under continuous cardiovascular monitoring. Nitroprussiate must, in addition, be given through a controlled infusion device, but ensures more flexible and safer control of blood pressure. Dihydralazine may produce headache. This side effect occurs very early and is hardly compatible with continuation of treatment. Long term side effects are very uncommon or strictly biological for dosages below 200 mg/day. With currently used dosages (20 to 60 mg per day) minoxidil consistently produces hypertrichosis, outruling its protacted use in women.(ABSTRACT TRUNCATED AT 250 WORDS)