Pharmacology. Nitroprusside is an ultra–short-acting, titratable parenteral hypotensive agent that acts by directly relaxing vascular smooth muscle as a nitric oxide donor. Both arterial dilation and venous dilation occur; the effect is more marked in patients with hypertension. A small increase in heart rate may be observed in hypertensive patients. Intravenous administration produces a nearly immediate onset of action, with a duration of effect of 1–10 minutes. Resistance may occur with high renin activity. Nitroprusside is metabolized rapidly, with a serum half-life of about 1–2 minutes. Cyanide is produced during metabolism and is converted to the less toxic thiocyanate. Thiocyanate has a half-life of 2–3 days and accumulates in patients with renal insufficiency.

Indications

1. 
   

   Rapid control of severe hypertension (eg, in patients with stimulant intoxication or monoamine oxidase inhibitor toxicity).

   
   
2. 
   

   Arterial vasodilation in patients with ergot-induced peripheral arterial spasm.

Contraindications

1. 
   

   Compensatory hypertension–for example, in patients with increased intracranial pressure (eg, hemorrhage or mass lesion) or patients with coarctation of the aorta. If nitroprusside is required in such patients, use with extreme caution.

   
   
2. 
   

   Use with caution in patients with hepatic insufficiency because cyanide metabolism may be impaired.

Adverse effects

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