Vasodilator — Nitric Oxide Donor (IV) Pregnancy: Avoid — fetal cyanide toxicity; risk outweighs benefit; use labetalol or hydralazine as safer alternatives in hypertensive emergency of pregnancy

Sodium Nitroprusside

Brand names: Nipride, Nitropress

Adult dose

Dose: 0.3–10 mcg/kg/min IV infusion; usual starting dose 0.5–1 mcg/kg/min; titrate to target MAP

Route: IV infusion via central line

Frequency: Continuous infusion

Max: 10 mcg/kg/min; limit duration at high doses (cyanide toxicity risk >72 hours or >3 mcg/kg/min)

Potent, balanced arterial and venous dilator. Used for hypertensive emergency, aortic dissection (reduce MAP to 60–70 mmHg), post-cardiac surgery afterload reduction, controlled hypotension in surgery. Must be protected from light (photodegradation). Delivered via dedicated syringe pump — do not mix with other drugs.

Paediatric dose

Dose: 0.3–4 mcg/min/kg

Route: IV infusion

Frequency: Continuous

Max: 4 mcg/kg/min (lower max than adults due to cyanide risk)

Paediatric hypertensive emergency or controlled hypotension — specialist guidance required. Protect from light. Monitor for cyanide toxicity.

Dose adjustments

Renal

Use with extreme caution — thiocyanate accumulates in renal failure; monitor thiocyanate levels; avoid prolonged use.

Hepatic

Use with caution — hepatic metabolism of cyanide to thiocyanate may be impaired in severe liver disease.

Paediatric weight-based calculator

Patient weight (kg)

Paediatric hypertensive emergency or controlled hypotension — specialist guidance required. Protect from light. Monitor for cyanide toxicity.

Clinical pearls

Cyanide toxicity monitoring: measure plasma lactate and arterial blood gas during prolonged high-dose infusion; rising lactate (>10 mmol/L), metabolic acidosis, or haemodynamic deterioration despite increasing dose = cyanide toxicity; antidote: hydroxocobalamin (Cyanokit) 5 g IV over 15 min
Aortic dissection: nitroprusside is the agent of choice for rapid BP reduction — combine with IV beta-blocker (esmolol or labetalol) to prevent reflex tachycardia which worsens dissection; target SBP 100–120 mmHg, HR <60 bpm
Light protection: sodium nitroprusside degrades rapidly in light — wrap infusion bag and line in aluminium foil or use light-protected set; solution turns blue/green = degraded, discard immediately
Sodium thiosulphate co-infusion (5–10 mg/kg/min) can be given concurrently at high doses to accelerate cyanide detoxification — converts cyanide to thiocyanate (less toxic); monitor thiocyanate levels if used for >72h

Contraindications

Compensatory hypertension (coarctation of aorta, AV shunt)
Severe hepatic impairment (relative — cyanide metabolism impaired)
Leber's hereditary optic neuropathy
Tobacco amblyopia
Vitamin B12 deficiency

Side effects

Cyanide toxicity (high doses >3 mcg/kg/min or prolonged use >72h): lactic acidosis, confusion, seizures, cardiac arrest
Thiocyanate accumulation (renal failure): tinnitus, blurred vision, hypothyroidism
Excessive hypotension
Reflex tachycardia
Nausea (with rapid BP reduction)
Methaemoglobinaemia (rare)

Interactions

Other antihypertensives (additive hypotension)
Phosphodiesterase inhibitors (sildenafil etc. — profound hypotension — avoid)
Hydroxocobalamin (cyanide antidote — administering this inactivates nitroprusside; use sequentially if cyanide toxicity develops)

Monitoring

Continuous intra-arterial BP monitoring (A-line mandatory)
Plasma lactate (cyanide toxicity marker)
Serum thiocyanate if renal impairment or infusion >72h
ABG (metabolic acidosis = cyanide toxicity)
ECG

Reference: BNFc; BNF 90; ESC Guidelines on Acute Aortic Syndromes 2024; BHS/NICE Hypertensive Emergency Guidelines; BNFc; MHRA SPC Nipride. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

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