• Understand PK and PD well.
  1. It functions as an intravenous vasodilator.
    • It is a complex consisting of cyanide group, iron and a nitroso group.
  1. It releases NO, which stimulates guanylyl cyclase to increase cGMP levels. This leads to both venodilation and arteriolar dilation.
    • In the absence of heart failure, there is a fall in BP due to decreased vascular resistance. Cardiac output generally does not change (or it may fall slightly).
    • In patients with heart failure and low cardiac output, SNP may increase cardiac output by decreasing afterload.
  1. IV only.
    • It has a T ½ of two minutes, and overall duration of action of 1-10 minutes.
    • Its metabolite thiocyanate has a T ½ of 3 days.
  1. SNP is taken up by RBCs and readily metabolized to release NO and cyanide.
    • Cyanide is metabolized in the liver by the mitochondrial enzyme rhodanase to thiocyanate.
    • Thiocyanate is then distributed to the extracellular fluid and excreted renally.
  1. Renal
  1. Hypertensive emergency
Special precautions
  1. Renal impairment (due to reduced excretion of thiocyanate)
  2. High doses and long infusion times may cause toxicity
Adverse effects
  1. Excessive fall in BP (requires arterial line to use)
  2. Cyanide toxicity – metabolic acidosis, arrhythmia, tachypnea, pink skin and dilated pupils.
  3. Thiocyanate toxicity – CNS effects, e.g. ataxia, weakness, disorientation, psychosis, N/V and seizures.
  1. Sodium thiosulphate provides a sulphur group to assist with cyanide metabolism.
  2. Hydroxycobalamin (Vit B12) can also be used – it is metabolized to a non-toxic byproduct known as cyanocobalamin.
Withdrawal states
Special notes