Diazoxide parenteral

Hypertension, sometimes severe, may occur. (See Nitroprusside and Diazoxide, Parenteral in the Agents for Hypertensive Emergencies section.)... 

This class of drugs includes the oral vasodilators, hydralazine and minoxidil, which are used for long-term outpatient therapy of hypertension the parenteral vasodilators, nitroprusside, diazoxide, and fenoldopam, which are used to treat hypertensive emergencies the calcium channel blockers, which are used in both circumstances and the nitrates, which are used mainly in angina (Table 11-3). 

Diazoxide is an effective and relatively long-acting parenterally administered arteriolar dilator that is occasionally used to treat hypertensive emergencies. Injection of diazoxide results in a rapid fall in systemic vascular resistance and mean arterial blood pressure associated with substantial tachycardia and increase in cardiac output. Studies of its mechanism suggest that it prevents vascular smooth muscle contraction by opening potassium channels and stabilizing the membrane potential at the resting level. 

Diazoxide is a potent vasodilator chemically resembling the thiazides, but it is not a diuretic. Diazoxide can be administered both parenterally and orally. Caution has been stressed when diazoxide is administered as an intravenous bolus into the pulmonary artery because the solution is highly alkaline (pH 11.6) and irritating to vascular tissue (Cotter and Honey, 1980). In one study with chronic oral diazoxide administration (300-600 mg/day), five of seven patients had important side effects including diabetes mellitus, fluid retention, nausea, vomiting, and postural hypertension that required discontinuation of the drug (Wise, 1983). 

Diazoxide is a parenteral, rapid, and direct-acting vasodilating antihypertensive used in hypertensive emergencies. An IV injection can drop blood pressure by as much as 80 mmHg in 5 minutes. Unlike sodium nitroprusside, however, venous dilation is not part of its mechanism. Chemically it is a benzothiadiazide without the sulfamoyl function at the 7 position (see diuretics). In fact, diazoxide is not a diuretic. Chronic use of diazoxide reflexly increases renin release, which actually counteracts the antihypertensive effect of the drug by expanding the volume of circulating fluid. 

Diazoxide, is used orally as an antihypoglycemic agent. Used parenterally, it acts as an arterial vasodilator and acts to selectively relax arterial smooth muscle. Because venous capacitance is not affected, systolic pressure is reduced more than diastolic pressure, and pulse pressure is reduced. 

C. Nitroprusside and Diazoxide These parenteral vasodilators are used in hypertensive emergencies. Nitroprusside is a short-acting agent (duration of action is a few minutes) that must be infused continuously. The drug s mechanism of action involves the release of nitric oxide (from the molecule itself, not from the endothelium), which stimulates guanylyl cyclase and increases cGMP concentration in smooth muscle. The toxicity of nitroprusside includes excessive hypotension, tachycardia, and, if infusion is continued over several days, cumulation of cyanide or thiocyanate ions in the blood. 

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