sodium nitroprusside

see also:

• vasodilators
• antihypertensives

• potent, rapid direct-acting that greatly reduces arterial blood pressure
• relaxes both venous and arterial circulation
• half-life of nitroprusside is 2 minutes (metabolised to cyanide by eryythrocytes then to thiocyanate in the liver)
• half-life of thiocyanate toxic metabolite is 3 days (excreted in kidneys)

• must be given by iv infusion
• onset within minutes
• duration of action 1-10 minutes after cessation of infusion
• initial dose for hypertensive emergency is 0.3mcg/kg/min slowly titrated to max. 10mcg/kg/min if needed, although infusion rates > 2mcg/kg/min may risk accumulation of cyanide ions
• solution must be prepared fresh using 5% glucose, and protected from light, and discarded after 24hrs or if it turns blue, green or dark red (it should have a faint brown tinge)

• hypotension
• hypersensitivity to nitroprusside
• cerebrovascular disease
• coronary artery disease
• liver disease
• renal impairment
• B12 deficiency

• hypothyroidism
• hypothermia
• lung disease

• hypotension
• tachycardia
• dizziness
• sweating
• headaches
• anxiety
• abdominal cramps
• hypothyroidism
• flushing
• rash
• muscle twitching

• cyanide toxicity may cause:
  • tachycardia, sweating, hyperventilation, metabolic acidosis, hypotension, arrythmias, death.
  • Rx includes ceasing infusion, consider, iv sodium nitrite and sodium thiosulphate to increase metabolism to thiocyanate

• thiocyanate toxicity is rarely a problem but may cause:
  • nausea, SOB, blurred vision, confusion, psychosis and tinnitus
  • Rx may be haemodialysis