Mechanism of action
Dexamethasone binds to cytoplasmic glucocorticoid receptors, forming a receptor-ligand complex that translocates to the nucleus and modulates gene transcription. It upregulates anti-inflammatory proteins such as lipocortin-1 (annexin-1), which inhibits phospholipase A2 and reduces arachidonic acid production, thereby decreasing synthesis of prostaglandins and leukotrienes.
Dexamethasone downregulates pro-inflammatory mediators including cytokines (IL-1, IL-6, TNF-α), adhesion molecules, and chemokines. It stabilizes lysosomal membranes, inhibits leukocyte migration, and suppresses T-cell and macrophage function. At pharmacologic doses, it exerts potent anti-inflammatory, immunosuppressive, and antiproliferative effects.
Dexamethasone has negligible mineralocorticoid activity due to its fluorination at the 9-alpha position, which prevents binding to mineralocorticoid receptors. Its long half-life (36–54 hours) is due to minimal 11-beta-hydroxysteroid dehydrogenase metabolism and low protein binding relative to other corticosteroids.
- Dexamethasone is 25 times more potent than hydrocortisone and has minimal mineralocorticoid activity.
- Drug of choice for cerebral edema due to lack of sodium retention.
- Used for fetal lung maturation in preterm labor between 24–34 weeks gestation.
- Adjunctive therapy in bacterial meningitis reduces hearing loss; give before or with first antibiotic dose.
- Dexamethasone suppression test: 1 mg at 11 PM, measure 8 AM cortisol; normal suppression (≤1.8 µg/dL, varies by assay) rules out Cushing syndrome.
- Reduces mortality in hospitalized COVID-19 patients requiring supplemental oxygen.
- Long half-life (36–54 hours) due to minimal hepatic inactivation.
- Prolonged use (>2–3 weeks) suppresses HPA axis; taper to avoid adrenal crisis.
Indications
Dexamethasone is used across a wide range of inflammatory, allergic, immunologic, and neoplastic conditions.
Neurologic
- Cerebral edema: Drug of choice due to minimal mineralocorticoid effects and reduced risk of fluid retention
- Increased intracranial pressure from brain tumors or trauma
- Prevention of postoperative edema after neurosurgery
Respiratory
- Acute asthma exacerbation and chronic obstructive pulmonary disease exacerbation
- Croup (laryngotracheobronchitis) in children
- Prevention of bronchopulmonary dysplasia in preterm infants
Infectious and inflammatory
- Bacterial meningitis (adjunctive): reduces neurologic sequelae, especially hearing loss
- COVID-19 in hospitalized patients requiring supplemental oxygen or mechanical ventilation
- Severe allergic reactions and anaphylaxis (adjunctive)
Endocrine
- Adrenal insufficiency (acute or chronic replacement)
- Congenital adrenal hyperplasia
- Dexamethasone suppression test (diagnostic)
Oncologic
- Antiemetic in chemotherapy-induced nausea and vomiting
- Palliative treatment of cerebral metastases and spinal cord compression
- Management of multiple myeloma and lymphoma
Obstetric
- Fetal lung maturation in preterm labor (24–34 weeks gestation)
Other
- Rheumatologic and autoimmune diseases
- Ophthalmic inflammation (uveitis, keratitis)
- Dermatologic conditions (severe eczema, contact dermatitis)
Pharmacokinetics
Absorption: Well absorbed orally (bioavailability >80%). Peak plasma concentrations occur within 1–2 hours. Also available as IV, IM, topical, and ophthalmic formulations.
Distribution: Widely distributed. Crosses the blood-brain barrier and placenta. Moderate plasma protein binding (~70%).
Metabolism: Hepatic metabolism via CYP3A4. Dexamethasone undergoes minimal 11-beta-hydroxysteroid dehydrogenase inactivation, contributing to its long duration of action.
Elimination: Half-life is 36–54 hours, significantly longer than other corticosteroids. Excreted in urine as metabolites.
Special populations: Dosing adjustments are generally not required in renal or hepatic impairment, though caution is advised in severe hepatic disease.
Adverse effects
Adverse effects are dose- and duration-dependent. Short courses (≤7 days) are generally well tolerated.
Endocrine and metabolic
- HPA axis suppression: Prolonged use suppresses endogenous cortisol production; abrupt withdrawal can precipitate adrenal crisis
- Hyperglycemia: Worsens diabetes; may precipitate steroid-induced diabetes
- Cushing syndrome: Moon facies, buffalo hump, central obesity, purple striae with chronic use
- Growth retardation in children
- Dyslipidemia
Musculoskeletal
- Osteoporosis: Increased fracture risk with long-term use
- Avascular necrosis (especially femoral head)
- Myopathy (proximal muscle weakness)
Gastrointestinal
- Peptic ulcer disease (especially when combined with NSAIDs)
- Gastrointestinal bleeding
- Pancreatitis (rare)
Psychiatric
- Mood changes, insomnia, irritability
- Psychosis, mania, depression (dose-related)
Infectious
- Immunosuppression: increased risk of bacterial, fungal, viral, and opportunistic infections
- Reactivation of latent tuberculosis
Ophthalmic
- Posterior subcapsular cataracts
- Increased intraocular pressure and glaucoma
Cardiovascular
- Hypertension
- Sodium and water retention (minimal with dexamethasone)
Dermatologic
- Skin thinning, easy bruising, impaired wound healing
- Acne, hirsutism
Other
- Leukocytosis (neutrophilia with lymphopenia)
- Hypokalemia (rare)
Contraindications and warnings
Absolute contraindications:
- Systemic fungal infections (unless treating life-threatening condition with antifungal coverage)
- Hypersensitivity to dexamethasone or formulation components
Relative contraindications and cautions:
- Active or latent tuberculosis: risk of reactivation
- Viral infections (herpes simplex keratitis, varicella, measles): may worsen or disseminate
- Recent myocardial infarction: risk of myocardial rupture
- Peptic ulcer disease or gastrointestinal bleeding
- Psychosis or severe psychiatric disorders
- Diabetes mellitus: monitor glucose closely
- Osteoporosis or fracture risk
Serious warnings: While dexamethasone does not carry a black box warning distinct from general corticosteroid class warnings, all systemic corticosteroids including dexamethasone carry serious FDA warnings about immunosuppression with increased infection risk, HPA axis suppression with potential for adrenal crisis upon withdrawal, and other significant adverse effects requiring careful monitoring.
Pregnancy: Category C (FDA). Crosses placenta; chronic use associated with cleft palate in animals. Used for fetal lung maturation when benefits outweigh risks. Monitor neonates for adrenal insufficiency if mother received chronic therapy.
Breastfeeding: Excreted in breast milk. High doses or prolonged use may suppress infant growth and interfere with endogenous corticosteroid production.
Withdrawal: Taper gradually after prolonged use (>2–3 weeks) to prevent adrenal crisis. HPA axis recovery may take months.
Drug interactions
CYP3A4 interactions
- Inducers (phenytoin, phenobarbital, rifampin, carbamazepine): decrease dexamethasone levels and efficacy
- Inhibitors (ketoconazole, ritonavir, clarithromycin): increase dexamethasone levels and toxicity risk
NSAIDs and anticoagulants
- Concurrent NSAIDs increase gastrointestinal bleeding risk
- May enhance or reduce anticoagulant effects (warfarin); monitor INR
Antidiabetic agents
- Reduces efficacy of insulin and oral hypoglycemics; adjust doses to maintain glycemic control
Vaccines
- Live vaccines (MMR, varicella, yellow fever): contraindicated during immunosuppression
- Inactivated vaccines: may have reduced immunogenicity
Diuretics and antihypertensives
- May antagonize effects of diuretics and antihypertensive agents
Other
- Increases clearance of salicylates
- May decrease levels of isoniazid and praziquantel
- Potentiates neuromuscular blockade with non-depolarizing muscle relaxants
Clinical pearls
- Cerebral edema: Dexamethasone is preferred over other steroids because it lacks mineralocorticoid activity and does not worsen cerebral edema via sodium retention.
- Dexamethasone suppression test: Used to diagnose Cushing syndrome. Low-dose test: 1 mg at 11 PM, measure 8 AM cortisol. Normal suppression (typically ≤1.8 µg/dL, though cutoffs vary by laboratory assay) rules out Cushing syndrome.
- Croup: A single dose significantly reduces symptom severity and need for hospitalization.
- Bacterial meningitis: Administer dexamethasone 15–20 minutes before or with the first antibiotic dose to reduce inflammation-mediated neurologic damage, especially in pneumococcal meningitis.
- COVID-19: Reduces mortality in hospitalized patients requiring oxygen but is harmful in mild disease without oxygen requirement.
- Fetal lung maturation: Given to mothers at risk of preterm delivery (24–34 weeks) to accelerate fetal surfactant production and reduce neonatal respiratory distress syndrome.
- HPA axis suppression: Risk increases with doses >7.5 mg/day (prednisone equivalent) for >3 weeks. Taper slowly and consider stress-dose steroids for surgery or illness.
- Antiemetic: Highly effective for chemotherapy-induced nausea, especially delayed nausea; often combined with 5-HT3 antagonists and NK1 antagonists.
- Potency: Approximately 25–30 times more potent than hydrocortisone, 6–7 times more than prednisone.
- No taper for short courses: Courses ≤7 days generally do not require tapering.
- Monitor: Blood glucose, blood pressure, bone density (with chronic use), electrolytes, growth in children, and signs of infection.
DEXAMETHASONE for side effects: Diabetes, Edema, Xtreme mood changes, Adrenal suppression, Myopathy, Electrolyte imbalance (hypokalemia), Thinning skin, Hypertension, Avascular necrosis, Sepsis risk, Osteoporosis, Necrosis (avascular), Eyes (cataracts, glaucoma).
Practice questions
1. A 4-year-old boy presents to the emergency department at 2 AM with a 2-day history of barky cough and inspiratory stridor. On examination, he has mild subcostal retractions and a respiratory rate of 32/min. Oxygen saturation is 97% on room air. Which of the following is the most appropriate initial pharmacologic intervention?
2. A 45-year-old woman with metastatic breast cancer and known brain metastases presents with worsening headache, nausea, and confusion over the past 3 days. MRI shows increased perilesional edema surrounding multiple brain metastases. Which property of dexamethasone makes it the preferred corticosteroid for managing her cerebral edema?
3. A 28-year-old man with HIV (CD4 count 450 cells/µL) develops acute bacterial meningitis and is started on appropriate antibiotics. His physician considers adding dexamethasone. The dexamethasone should be administered at which of the following time points to maximize benefit?
Frequently asked questions
How does dexamethasone work?
Dexamethasone binds to glucocorticoid receptors in the cytoplasm, translocates to the nucleus, and modulates gene transcription. It upregulates anti-inflammatory proteins and downregulates pro-inflammatory cytokines, inhibits phospholipase A2 (reducing prostaglandin and leukotriene synthesis), stabilizes cell membranes, and suppresses immune cell function. These combined actions result in potent anti-inflammatory and immunosuppressive effects.
What are the side effects of dexamethasone?
Common side effects include hyperglycemia, hypertension, mood changes, insomnia, and increased appetite. Long-term use can cause HPA axis suppression, Cushing syndrome, osteoporosis, avascular necrosis, cataracts, glaucoma, immunosuppression with increased infection risk, peptic ulcers, myopathy, and growth retardation in children. Short courses (≤7 days) are generally well tolerated with minimal side effects.
Is dexamethasone a controlled substance?
No, dexamethasone is not a controlled substance. It is a prescription corticosteroid medication but is not classified as a controlled drug under the US Controlled Substances Act or similar regulations in other countries. However, it requires a prescription because of its potent effects and potential for serious adverse effects with misuse or prolonged use.
Dexamethasone vs prednisone — what is the difference?
Dexamethasone is approximately 6–7 times more potent than prednisone and has a much longer half-life (36–54 hours vs 2–4 hours). Dexamethasone has minimal mineralocorticoid activity, making it preferred for cerebral edema, while prednisone has more mineralocorticoid effects. Dexamethasone is used for conditions requiring long-acting potent anti-inflammatory effects, whereas prednisone is more commonly used for chronic inflammatory and autoimmune conditions requiring daily dosing.
Why is dexamethasone used in bacterial meningitis?
Dexamethasone is used as adjunctive therapy in bacterial meningitis to reduce inflammation-mediated neurologic damage. It decreases cytokine release and cerebral edema, which reduces complications such as hearing loss, especially in pneumococcal meningitis. For maximum benefit, it should be given 15–20 minutes before or with the first dose of antibiotics. It does not treat the infection itself but mitigates the harmful inflammatory response.
Conditions it is used for
Related drugs
Sources and further reading
DailyMed (FDA labels)StatPearls (NCBI Bookshelf)MedlinePlusWHO ATC/DDD index: A01AC02WHO ATC/DDD index: C05AA09
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.