Pharmacology · Corticosteroids (glucocorticoids)
Dexamethasone !
A potent, long-acting corticosteroid with almost no salt retention, used for severe inflammation, brain oedema and adrenal testing.
Updated 2026-11-01
The figure shows dexamethasone itself in the ligand-binding domain of the human glucocorticoid receptor, with a coactivator peptide.
Mechanism of action
Dexamethasone is a fluorinated glucocorticoid that binds the glucocorticoid receptor strongly. The complex enters the nucleus, switches on anti-inflammatory genes and represses NF-κB and AP-1, so cytokines and inflammatory mediators fall. It has practically no mineralocorticoid action and a long biological duration, and it suppresses ACTH, the basis of the dexamethasone suppression test.
- Dexamethasone binds the glucocorticoid receptor in the cytoplasm
- The drug-receptor complex moves into the nucleus
- It switches on anti-inflammatory genes and represses NF-κB and AP-1
- Fewer cytokines, prostaglandins and immune cells reach the tissue
Pharmacokinetics
- Absorption
- Well absorbed by mouth; injectable, eye and ear forms also exist
- Metabolism
- In the liver by CYP3A4, so inducers and inhibitors change its levels
- Half-life
- Long-acting: its biological effect lasts much longer than hydrocortisone's
Indications
- Cerebral oedema from brain tumours, craniotomy or head injury
- Dexamethasone suppression test in the study of Cushing syndrome Cushing syndrome →
- Severe asthma exacerbations and other allergic states Asthma →
- Rheumatic diseases such as rheumatoid arthritis Rheumatoid arthritis →
- Acute exacerbations of multiple sclerosis Multiple sclerosis →
- Palliative care of leukaemias and lymphomas
Adverse effects
Common
- Insomnia and restlessness
- Increased appetite and weight gain
- Hyperglycaemia
- Stomach upset
- Acne and easy bruising
Contraindications
- Systemic fungal infections
- Hypersensitivity to the product
- Live or live attenuated vaccines during immunosuppressive doses
Key interactions
- CYP3A4 inducers (rifampicin, phenytoin, carbamazepine, barbiturates)
- Faster clearance and a weaker corticosteroid effect
- Strong CYP3A4 inhibitors (ketoconazole)
- Higher corticosteroid levels and more side effects
- Aspirin and other NSAIDs
- Higher risk of gastrointestinal ulcer and bleeding
- Potassium-depleting drugs (loop or thiazide diuretics, amphotericin B)
- Hypokalaemia; with digoxin, more risk of arrhythmia
- Warfarin
- The anticoagulant response changes; INR is checked more often
What is monitored
- Blood glucose
- Blood pressure and weight
- Potassium
- Signs of infection
- Eye pressure and bone density with long use
Administration and safety
- Comes as tablets, oral solution and injection (sodium phosphate); the routes are not interchangeable without an order
- Oral forms are usually given with food to reduce stomach upset
- After prolonged use the drug is tapered, never stopped suddenly
Nursing care
- Check glucose, especially in people with diabetes; corticosteroids raise it
- Watch for infection: fever and other signs may be blunted
- Watch mood and sleep; report agitation, depression or confusion
- Teach that a long course is not stopped suddenly; it is tapered under medical supervision
- Ask about black or tarry stools, a sign of digestive bleeding
Pregnancy and breastfeeding
Used in pregnancy when the benefit justifies it; newborns of mothers on substantial doses are watched for adrenal insufficiency.
Test yourself
Think of the answer, then tap the question to see it.
Why is dexamethasone, and not hydrocortisone, used in the suppression test for Cushing syndrome?
It suppresses ACTH strongly but is not measured by standard cortisol assays, so a fall in measured cortisol reflects the patient's own adrenal output.
Why is dexamethasone preferred for cerebral oedema around a brain tumour?
It is potent and long-acting with practically no salt and water retention, so it reduces vasogenic oedema without adding fluid load.
A patient on dexamethasone starts rifampicin. What happens to the steroid effect?
It weakens: rifampicin induces CYP3A4 and speeds dexamethasone clearance.
Related drugs
Related conditions
← Back to the class: Corticosteroids (glucocorticoids)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Dexamethasone: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2017); DailyMed - DEXAMETHASONE tablet (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.