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Vasodilator (Nitric Oxide Donor) Pregnancy: Avoid — cyanide toxicity risk to fetus

Sodium Nitroprusside

Brand names: Nipride

Adult dose

Dose: 0.3–10 mcg/kg/min IV infusion, titrated to BP response
Route: IV infusion (protect from light — photodegrades)
Frequency: Continuous infusion
Max: 10 mcg/kg/min; do not exceed 72 hours at high doses (cyanide toxicity)
For hypertensive emergency, acute HF with severe mitral regurgitation/aortic regurgitation, or controlled hypotension in surgery. Monitor for cyanide toxicity with high doses or prolonged use.

Paediatric dose

Dose: 0.3 mcg/min/kg
Route: IV infusion
Frequency: Continuous
Max: 8 mcg/kg/min
Concentration: Variable — dilute in 5% dextrose, protect from light mcg/min/ml
Starting dose 0.3 mcg/kg/min, titrate carefully. Maximum 3 mcg/kg/min to reduce cyanide risk in children.

Dose adjustments

Renal

Thiocyanate accumulates in renal failure — monitor levels; limit duration

Hepatic

Cyanide metabolism impaired in hepatic failure — increased toxicity risk

Paediatric weight-based calculator

Starting dose 0.3 mcg/kg/min, titrate carefully. Maximum 3 mcg/kg/min to reduce cyanide risk in children.

Clinical pearls

  • Must be protected from light — wrap syringe and tubing in foil; degrades within hours when exposed
  • Cyanide antidote (hydroxocobalamin) should be available when using high doses
  • Rebound hypertension can occur on abrupt discontinuation — taper slowly
  • Reserved for specialist use in HDU/ICU only due to complexity and toxicity monitoring requirements

Contraindications

  • Compensatory hypertension (coarctation, AV shunting)
  • High output cardiac failure
  • Congenital optic atrophy or tobacco amblyopia
  • Vitamin B12 deficiency

Side effects

  • Hypotension (profound)
  • Cyanide toxicity (tachyphylaxis, lactic acidosis, altered consciousness)
  • Thiocyanate toxicity with prolonged use (>72h)
  • Nausea
  • Methemoglobinaemia (rare)

Interactions

  • Antihypertensives — additive hypotension
  • PDE5 inhibitors — profound hypotension
  • Sildenafil — contraindicated combination

Monitoring

  • Continuous arterial blood pressure monitoring
  • Acid-base status (lactic acidosis suggests cyanide toxicity)
  • Thiocyanate levels with prolonged use
  • Blood pressure closely during titration

Reference: BNFc; BNF; ESC Hypertension Guidelines 2023. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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