Hydralazine has a direct effect on the smooth muscle in arterial walls. The molecular mechanism is unknown. It decreases the tone of the musculature in the wall, especially in arterioles and thus diminishes the peripheral resistance. The body reacts on the vasodilation by stimulating the sympathetic nervous system. This counter effect can be rather serious and causing increase in heart minute volume and tachycardia.
Hydralazine is often used in combination with a β-blocker. Hydralazine can be applied in case of hypertension and (pre)eclampsia during pregnancy.
Several studies have confirmed that hydralazine use during gestation is not associated with congenital malformations.
Check also the topic on direct vasodilators in cardiology section.
I. Hydralazine during pregnancy should be prescribed with a β-blocker.
II. Hydralazine can also be used in patients with chronic heart failure.
Extra info: Hydralazine is commonly prescribed with a β-blocker, but not for patients who are pregnant. β-blockers can harm the foetus. Also note that there’s no “betablockers” in this section of the TRC, so they’re not used in pregnancy. Hydralazine can indeed be used in patients with CHF who don’t respond to other therapies.