A hypertensive emergency is present when severe hypertension is associated with acute end-organ damage. Examples include hypertensive encephalopathy, acute pulmonary edema, aortic dissection, and rebound after abrupt withdrawal of antihypertensive medications. Immediate but careful reduction in blood pressure is often indicated in these settings. However, an excessive hypotensive response is potentially dangerous, possibly leading to ischemic complications such as stroke, myocardial infarction, or blindness. Thus, in patients who are severely hypertensive but asymptomatic, slower reductions in blood pressure may be achieved with oral agents. (See 'Oral drugs' below.)
The drugs that are used for the treatment of hypertensive emergencies are presented in this topic. The evaluation of patients with severe hypertension and the blood pressure goals in patients with hypertensive emergencies are presented elsewhere. (See "Evaluation and treatment of hypertensive emergencies in adults".)
A variety of parenteral and oral antihypertensive drugs are available for use in these patients (table 1) [1-5]. Few studies have compared these agents with one another, and all are tolerated reasonably well [6,7]. Thus, the drug of choice is often dictated by the type of hypertensive emergency and the local hospital formulary. (See "Malignant hypertension and hypertensive encephalopathy in adults" and "Evaluation and treatment of hypertensive emergencies in adults".)
Nitrates — Nitrovasodilators such as nitroprusside and nitroglycerin provide nitric oxide that induces vasodilatation (of both arterioles and veins) via generation of cyclic GMP, which then activates calcium-sensitive potassium channels in the cell membrane .
Nitroprusside — Sodium nitroprusside, when administered by intravenous infusion, begins to act within one minute or less, and once discontinued, its effects disappear within 10 minutes or less. Frequent monitoring is required since this drug can produce a sudden and drastic drop in blood pressure.