Hydralazine

Hydralazine is a medication that relaxes arterial smooth muscle, lowering blood pressure and reducing the heart’s workload. It is used for hypertension and, with isosorbide dinitrate, for selected cases of heart failure.

Arteriolar vasodilation: Widening of small arteries that reduces resistance to blood flow. Hydralazine primarily lowers blood pressure by relaxing arteriolar smooth muscle.
Hypertension: Persistently elevated arterial blood pressure that increases cardiovascular risk. Hydralazine is used to lower blood pressure, especially in selected severe or difficult-to-control cases.
Minoxidil: A potent arteriolar vasodilator used for severe hypertension and, topically, hair loss. Like hydralazine, it can cause reflex tachycardia and fluid retention, but has different adverse effects and uses.
Vascular smooth muscle: The contractile muscle cells in blood-vessel walls that regulate vessel diameter. Hydralazine lowers vascular resistance by relaxing this tissue, especially in small arteries.
Nitric oxide signaling: Cell signaling in which nitric oxide activates soluble guanylate cyclase and raises cyclic GMP. Nitric oxide pathways are among the proposed contributors to hydralazine’s vascular smooth-muscle relaxation.
Heart failure: A clinical syndrome in which the heart cannot meet the body's needs without elevated filling pressures. Hydralazine paired with isosorbide dinitrate can improve outcomes in selected patients with reduced-ejection-fraction heart failure.
Sodium nitroprusside: A rapidly acting intravenous vasodilator used for controlled blood-pressure reduction in monitored settings. Unlike hydralazine’s longer, less predictable effect, nitroprusside can be titrated rapidly.
Systemic vascular resistance: The resistance that the systemic circulation presents to blood flow from the heart. Arteriolar dilation reduces this resistance and lowers the pressure against which the heart pumps.
Baroreceptor reflex: A rapid autonomic response that adjusts heart rate and vascular tone when blood pressure changes. A fall in pressure can trigger reflex tachycardia during hydralazine treatment.
Isosorbide dinitrate: A nitrate medication that relaxes vascular smooth muscle and reduces cardiac preload. Combined with hydralazine, it provides complementary arterial and venous dilation in heart failure treatment.

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MethyldopaCompared with: It is used in acute severe hypertension, unlike methyldopa’s usual ongoing oral role.