Sodium Nitroprusside

Nitroprusside is injected into a vein through an infusion pump. You will receive this injection in a clinic or hospital setting.

Nitroprusside is usually given for as long as needed until your body responds to the medication.

Your breathing, blood pressure, oxygen levels, and other vital signs will be watched closely while you are receiving nitroprusside. Your blood and urine may also need to be tested during treatment.

Tell your caregivers at once if you think you have received too much of this medicine. Overdose symptoms may include extreme dizziness, nausea and vomiting, muscle twitching, rapid breathing, fast or pounding heartbeat, and feeling like you might pass out.

Since nitroprusside is given as needed by a healthcare professional, you are not likely to miss a dose.

Hypertensive Crises

For immediate reduction of BP in hypertensive emergencies.207 500 502 542 600 Administer with other longer-acting hypotensive agents to minimize the duration of nitroprusside therapy.600 Use in carefully selected patients because of potential for serious toxicity (see Cautions).542

Can be used for most hypertensive emergencies (e.g., hypertensive encephalopathy, MI, unstable angina pectoris, acute left ventricular failure with pulmonary edema, eclampsia, aortic dissection).207 500

May be considered in the treatment of hypertensive emergencies associated with stimulant (e.g., amphetamines, methamphetamines, cocaine, phencyclidine, ephedrine) toxicity.207

Use caution if high intracranial pressure or azotemia is present.500

Other antihypertensive agents (e.g., hydralazine, labetalol, nifedipine) preferred for management of acute severe hypertension in preeclampsia; reserve sodium nitroprusside for treatment failures.208 209 500 540

Contraindicated in compensatory hypertension (e.g., arteriovenous shunt or coarctation of the aorta).600 (See Contraindications under Cautions.)

Heart Failure and Low-Output Syndromes

Management of acute decompensated (e.g, congestive) heart failure.207 524 600

May be considered an adjunct to diuretic therapy for relief of dyspnea in patients hospitalized for acutely decompensated heart failure who do not have symptomatic hypotension.524

Particularly useful in severe heart failure caused by regurgitant valvular lesions of aortic insufficiency and mitral regurgitation.206 Also useful in management of heart failure in patients with severe congestion and hypertension.524

Also useful for afterload reduction when left ventricular dysfunction is accompanied by right ventricular ischemia.202 600 Monitoring intra-arterial pressure is useful.202

Management of low-output syndromes associated with acute MI†; in many cases, other drugs (e.g., nitroglycerin, norepinephrine, dopamine, dobutamine) are preferred.202

In acute MI complicated by heart failure, nitroglycerin is the preferred vasodilator.202

Not indicated for the treatment of heart failure associated with reduced peripheral vascular resistance.600 (See Contraindications under Cautions.)

Controlled Hypotension

Used to produce controlled hypotension to reduce bleeding during surgery.600

Absorption

Onset

Immediate reduction in BP.600

Duration

BP begins to rise immediately when infusion is slowed or stopped; BP returns to pretreatment levels within 1–10 minutes.600

Distribution

Extent

Rapidly distributed.600

Elimination

Metabolism

Sodium nitroprusside is metabolized by combination with hemoglobin to form cyanmethemoglobin and cyanide.600

Essentially all cyanide in the blood is bound to methemoglobin until intraerythrocytic methemoglobin is saturated.600

Cyanide is enzymatically converted to thiocyanate by thiosulfate sulfurtransferase (a mitochondrial enzyme).207 600 This enzyme normally is present in excess quantities; the rate-limiting step in the conversion to thiocyanate is the availability of sulfur donors (e.g., thiosulfate, cystine, cysteine).600

Cyanide not otherwise removed binds to cytochromes.600

Elimination Route

Eliminated principally in urine as thiocyanate.600 Some cyanide is expired as hydrogen cyanide.600

Half-life

Sodium nitroprusside: Circulation half-life: 2 minutes.600

Thiocyanate: 3 days.600

Special Populations

Half-life of thiocyanate is increased in patients with renal failure.600

• The hypotensive action results from peripheral vasodilation caused by a direct action on vascular smooth muscle.600

• Direct vasodilation causes decreases in right and left ventricular filling (preload) resulting in relief of pulmonary congestion and reduced left ventricular volume and pressure.207 600 Arteriolar relaxation causes decreases in peripheral arterial resistance (afterload) resulting in enhanced systolic emptying with reduced left ventricular volume and wall stress and reduced myocardial oxygen consumption.207 600

• May exert a direct coronary vasodilator effect.600

• Induces renal vasodilation generally proportional to decreases in systemic BP with no appreciable changes in renal blood flow or GFR.600

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.