NCIt definition : A phthalazine derivative with antihypertensive effects. Hydralazine exerts its vasodilatory
effects through modification of the contractile state of arterial vascular smooth
muscle by altering intracellular calcium release, and interfering with smooth muscle
cell calcium influx. This agent also causes inhibition of phosphorylation of myosin
protein or chelation of trace metals required for smooth muscle contraction, thereby
resulting in an increase in heart rate, stroke volume and cardiac output.;