Dexamethasone

Dexamethasone

Perioperative indications for dexamethasone, a synthetic glucocorticoid, are expanding. It is has a well-established role in the prevention of postoperative nausea and vomiting. Synergistic analgesic, prolongation of regional anaesthesia and reduction in the severity of postoperative cognitive dysfunction can also be seen.

The safety of high dose dexamethasone is yet to be established. Benefits can still be seen at the low (<0.1mg/kg or 4mg) and intermediate (0.1-0.2mg/kg) range with fewer adverse effects. Their mechanism of action is not well understood but is likely linked to their anti-inflammatory properties. Dexamethasone can be given by the oral, intramuscular, perineural or intravenous route. For the remainder of this article, we will focus on the intravenous route.

Actions:

• Modulate inflammatory response
  • Prostaglandin antagonism
  • Inhibit interleukins, CRP, TNFα
• Reduce 5-HT (serotonin) release from the gut
• Endorphin release

Preparations:

• Clear colourless solution 8mg/2ml in a light protected vial

Benefits:

• Analgesia
  • Reduced postoperative pain
  • Prolonged local anaesthetic blockade
• Decreased postoperative nausea and vomiting
• Anti-inflammatory
• Reduced severity of postoperative cognitive dysfunction

Dose:

• Low: 4mg (or <0.1mg/kg)
• Intermediate: 0.1-0.2mg/ kg
• High: >0.2mg/kg

Onset:

• IV: 1hour

Kinetics:

• Peak plasma level 5 minutes
• Elimination half-life ~ 3hours
• Plasma protein binding ~ 77%
• Metabolized by the liver and kidneys
• Excreted in the urine

Caution:

• Diabetes
• Poor wound healing
• Reactivation of latent infections (immunosuppressive at higher doses)
• Perianal pain on injection
• Tumour Lysis Syndrome in patients with concurrent haematological disease