Peripheral dilating hypotensive agents

Presently on the U.S. market there are three compounds commonly considered as peripheral dilating hypotensive agents. These are hydralazine (I), placed on the market in 1953 by CIBA, diazoxide (II) from Schering in 1973 and sodium nitroprusside (III) made available by Roche in 1974. 

I. Mechanism of toxicity. All these drugs dilate peripheral arterioles to lower blood pressure. A reflex sympathetic response results in tachycardia and occasionally cardiac arrhythmias. Prazosin and other newer alpha-1-specific agents are associated with little or no reflex tachycardia however, postural hypotension is common, especially in patients with hypovolemia. 

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