Sodium Nitroprusside

How it works

It releases nitric oxide, which raises intracellular cyclic GMP in vascular smooth muscle to cause balanced arterial and venous dilatation, reducing both preload and afterload; its breakdown generates cyanide that is metabolised to thiocyanate.

Prescribing in practice

• Prolonged or high-rate infusion risks cyanide and thiocyanate accumulation and toxicity, so infusions should be kept as short and as low as effective, with caution in hepatic or renal impairment, and the solution must be protected from light.
• It can cause profound, rapid hypotension and reflex tachycardia, requiring continuous arterial blood-pressure monitoring, usually intra-arterial.
• Avoid abrupt cessation after prolonged use because of rebound hypertension; consult the SPC for preparation and administration.

Monitoring

Monitor blood pressure continuously (ideally intra-arterial), and watch for metabolic acidosis and other features of cyanide or thiocyanate toxicity, particularly with prolonged infusion or organ impairment.

Counselling the patient

• Explain that this medicine is given as a closely monitored drip in critical-care or theatre settings.
• Inform the team to protect the infusion from light and to watch for signs of toxicity with prolonged use.

Evidence & guidelines

Sodium nitroprusside is a long-established agent for hypertensive emergencies and controlled hypotension; refer to current prescribing references.