Hydralazine hydrochloride is a direct-acting vasodilator that is used as an antihypertensive agent.Target: OthersHydralazine hydrochloride (apresoline) is a direct-acting smooth muscle relaxant used to treat hypertension by acting as a vasodilator primarily in arteries and arterioles. By relaxing vascular smooth muscle, vasodilators act to decrease peripheral resistance, thereby lowering blood pressure and decreasing afterload. However, this only has a short term effect on blood pressure, as the system will reset to the previous, high blood pressure necessary to maintain pressure in the kidney necessary for natriuresis. The long term effect of antihypertensive drugs comes from their effects on the pressure natriuresis curve. It belongs to the hydrazinophthalazine class of drugs [1]. Hydralazine hydrochloride may reduce blood pressure when compared to placebo in patients with primary hypertension, however this data is based on before and after studies, not RCTs. Furthermore, its effect on clinical outcomes remains uncertain [2].

References:
[1]. Bourreli, B., et al., Additive effects of dihydralazine during enflurane or isoflurane hypotensive anaesthesia for spinal fusion. Can J Anaesth, 1988. 35(3 ( Pt 1)): p. 242-8.
[2]. Kandler, M.R., et al., Hydralazine for essential hypertension. Cochrane Database Syst Rev, 2010(8): p. CD004934.