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Drug Reference

dexamethasone

corticosteroid· Brands: Decadron, Dexsol, Maxidex, OzurdexIMIVPOSCTOP

Mechanism of action
Dexamethasone is a long-acting synthetic glucocorticoid that binds to cytoplasmic glucocorticoid receptors, regulating gene transcription to produce anti-inflammatory, immunosuppressive, and anti-allergic effects. It inhibits phospholipase A2, reducing prostaglandin and leukotriene synthesis, and suppresses cytokine production and immune cell activation. It also reduces ACTH release from the pituitary, leading to decreased endogenous cortisol synthesis.
Pharmacokinetics
Dexamethasone is well absorbed after oral administration, with bioavailability approaching 90%. It is extensively bound to plasma proteins (about 70-80%) and undergoes hepatic metabolism, primarily by CYP3A4, to inactive metabolites. The elimination half-life is approximately 36-72 hours, allowing once-daily dosing. It is excreted in urine, mainly as metabolites. Dexamethasone can also be administered intravenously, intramuscularly, subcutaneously, or topically; systemic absorption with topical use is minimal but possible.
Indications & dosing

Allergic reactions

For allergic reactions unresponsive to adrenaline; use with caution.

  • adult · IV: 4–8 mg once · For allergic reactions unresponsive to adrenaline; use with caution.

Cerebral oedema

Loading dose (10 mg IV) may be given in severe cases.

  • adult · IV: 4 mg every 6 hours · Loading dose (10 mg IV) may be given in severe cases.

Chemotherapy-induced nausea and vomiting (CINV)

Usually given as part of a combination antiemetic regimen.

  • adult · IV: 8–20 mg once · Usually given as part of a combination antiemetic regimen.

COVID-19 (severe)off-label

For up to 10 days; off-label use, follow local guidelines.

  • adult · PO: 6 mg once daily · For up to 10 days; off-label use, follow local guidelines.

Croup (laryngotracheobronchitis)

Single dose is effective; may be repeated after 24 hours if needed.

  • pediatric · PO: 0.15–0.6 mg/kg once · Single dose is effective; may be repeated after 24 hours if needed.
Contraindications & precautions
  • Systemic fungal infection · Do not use in patients with systemic fungal infections.
  • Known hypersensitivity to dexamethasone or any component
  • Live vaccines · Avoid live vaccines during immunosuppressive therapy; inactivated vaccines may be used but response may be reduced.
  • Peptic ulcer disease · May exacerbate ulcers; consider gastroprotection.
  • Diabetes mellitus · May impair glucose tolerance; monitor blood glucose.
  • Osteoporosis · Long-term use can worsen bone density; ensure adequate calcium and vitamin D.
  • Use the lowest effective dose for the shortest duration.
  • Do not stop suddenly; gradually reduce dose to avoid adrenal insufficiency.
  • Monitor blood glucose, blood pressure, and signs of infection.
  • Consider gastroprotection in patients at risk of peptic ulcer (e.g., with NSAIDs).
  • Avoid live vaccines during treatment.
  • Ensure adequate calcium and vitamin D intake to reduce osteoporosis risk.
Adverse effects
  • Increased appetite
  • Weight gain
  • Insomnia
  • Mood changes
  • Hyperglycaemia
  • Immunosuppressionserious
  • Peptic ulcerserious
  • Adrenal suppressionserious
  • Osteoporosisserious
  • Psychosisserious
Monitoring, pregnancy & toxicity
  • Blood glucose · Baseline, then regularly
  • Blood pressure · Baseline, then regularly
  • Serum electrolytes (including potassium) · Baseline, then periodically
  • Signs of infection · Throughout therapy
  • Adrenal function · During dose tapering
  • Bone density · If long-term use
  • Pregnancy: Use only if potential benefit outweighs risk. Dexamethasone crosses the placenta. Prolonged use during pregnancy may cause adrenal suppression in the neonate. Consider lower doses and monitor fetal growth.
  • Toxicity: Hyperglycaemia and hypertension · Monitor blood glucose and blood pressure; treat with insulin or antihypertensives if needed.
  • Toxicity: Adrenal suppression · Taper dose gradually to allow recovery of the HPA axis.
  • Toxicity: Immunosuppression and increased infection risk · Monitor for signs of infection; treat promptly if present.
  • Toxicity: Psychiatric disturbances (e.g. mood changes, psychosis) · Reduce dose or discontinue; provide supportive care.
Clinical notes
Dexamethasone is used for a wide range of conditions, including allergic reactions, asthma exacerbations, croup, cerebral oedema, and certain autoimmune and inflammatory diseases. It is also used in COVID-19 to reduce mortality in patients needing oxygen. The dose and route depend on the indication; for cerebral oedema, higher doses are used in conjunction with other agents. Long-term use is limited by systemic side effects such as hyperglycaemia, hypertension, osteoporosis, immunosuppression, and adrenal suppression. Tapering is necessary after prolonged therapy. For patients with diabetes or peptic ulcer, use with caution. Antifungals like ketoconazole may increase levels; CYP3A4 inducers may decrease them. Always consult the latest prescribing information and local guidelines.

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BNF; local formulary