dexamethasone
Brand: Decadron, DexPak, Baycadron
Prototype: prednisone
Drug Class: corticosteroid
Drug Family: corticosteroid
Subclass: synthetic glucocorticoid (long-acting) / no mineralocorticoid activity
Organ Systems: endocrinecns
Mechanism of Action
Long-acting glucocorticoid with approximately 25x the anti-inflammatory potency of cortisol; no mineralocorticoid activity (unlike prednisone); crosses BBB well; 5 mg dexamethasone equivalent to ~35 mg prednisone or ~175 mg hydrocortisone.
glucocorticoid receptor (GR)
Indications
- cerebral edema (brain tumors, head injury)
- anaphylaxis (adjunct after epinephrine)
- acute asthma exacerbation (outpatient single dose)
- croup (single IM/oral dose)
- CINV prevention (first-line component)
- septic shock (low-dose adjunctive — refractory shock)
- COVID-19 (patients requiring oxygen — RECOVERY trial)
- adrenal insufficiency testing (dexamethasone suppression test)
- multiple myeloma (component of treatment regimens)
Contraindications
- systemic fungal infections without antifungal coverage
- live vaccines with immunosuppressive doses
Adverse Effects
Common
- hyperglycemia
- insomnia
- psychosis / mood changes
- GI irritation
- increased appetite
Serious
- HPA axis suppression (even short high-dose courses)
- immunosuppression
- avascular necrosis (prolonged use)
- Cushing's syndrome (chronic use)
Pharmacokinetics (ADME)
| Absorption | Well absorbed orally; IV/IM formulation available |
| Distribution | Excellent CNS penetration; protein binding 77%; Vd ~0.8 L/kg |
| Metabolism | CYP3A4 to inactive metabolites |
| Excretion | Renal |
| Half-life | 3.5 hours (plasma); biological half-life 36–54 hours |
| Onset | Rapid (IV/IM); 1–2 hours (oral) |
| Peak | 1 hour (IV); 1–2 hours (oral) |
| Duration | 36–54 hours |
| Protein Binding | 77% |
| Vd | ~0.8 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| CYP3A4 inducers | reduce dexamethasone levels | moderate |
| diabetes medications | hyperglycemia from dexamethasone increases insulin requirements dramatically (especially high-dose pulse) | moderate |
Nursing Considerations
- For cerebral edema: 10 mg IV loading dose followed by 4 mg IV q6h; reduces peritumoral vasogenic edema (not cytotoxic edema from stroke); onset of benefit 12–24 hours
- Single-dose IM or oral dexamethasone (0.6 mg/kg) is now preferred for croup — long duration of action allows single dosing with equivalent efficacy to multiple doses of oral prednisolone
- Monitor blood glucose closely, especially in diabetic patients — dexamethasone causes significant hyperglycemia peaking 4–8 hours after dosing; insulin adjustments are almost always required
- Unlike prednisone, dexamethasone has no mineralocorticoid activity — it does NOT raise blood pressure or cause sodium/water retention at typical doses
Clinical Pearls
- The RECOVERY trial (2020) established dexamethasone 6 mg/day for 10 days as standard of care for COVID-19 patients requiring supplemental oxygen or mechanical ventilation — the first treatment shown to reduce mortality (22% relative risk reduction)
- Dexamethasone is used as the reference steroid for CINV prophylaxis because of its long half-life (once-daily dosing), potency, and ability to cross the BBB (central anti-emetic mechanisms)
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.
Acute Asthma Exacerbation (outpatient Single Dose) Adrenal Insufficiency Testing (dexamethasone Suppression Test) Anaphylaxis (adjunct After Epinephrine) Cerebral Edema (brain Tumors, Head Injury) CINV Prevention (first-line Component) Corticosteroid COVID-19 (patients Requiring Oxygen — RECOVERY Trial) Croup (single IM/oral Dose) Multiple Myeloma (component Of Treatment Regimens) Septic Shock (low-dose Adjunctive — Refractory Shock)