vasodilatator

Vasodilators are substances or medications that cause dilation of blood vessels by relaxing vascular smooth muscle. This widening increases blood flow and lowers systemic vascular resistance and blood pressure. Vasodilation can be endothelium-dependent, often mediated by nitric oxide and prostacyclin signaling, or endothelium-independent, acting directly on smooth muscle ion channels.

Drugs differ in their vascular targets. Nitrates (for example, nitroglycerin and isosorbide dinitrate) predominantly dilate veins; calcium channel blockers (such as amlodipine and diltiazem) mainly dilate arteries; hydralazine and minoxidil are direct smooth-muscle relaxants; nitroprusside and diazoxide can dilate both arteries and veins. Indirect-acting agents include ACE inhibitors and ARBs, which promote vasodilation by lowering angiotensin II–mediated tone, and phosphodiesterase-5 inhibitors (sildenafil, tadalafil), which enhance cGMP-mediated relaxation. Prostacyclin analogs (epoprostenol) are used for certain forms of pulmonary hypertension.

Indications include hypertension, angina, and heart failure with reduced ejection fraction, as well as pulmonary arterial hypertension and erectile dysfunction in the case of PDE5 inhibitors. Nitrates are commonly used for angina; nitrates with PDE5 inhibitors must be avoided due to risk of severe hypotension.

Common adverse effects are hypotension, dizziness, headaches, flushing, and edema; reflex tachycardia may occur with some agents. Drug interactions and conditions that impair compensatory responses to vasodilation require careful management, and routes of administration range from oral and transdermal to intravenous and inhaled, with pharmacokinetics varying by substance.