1. Clinical Overview
Dexamethasone is a potent, long-acting synthetic glucocorticoid with anti-inflammatory, immunosuppressive, anti-allergic, and anti-proliferative properties. It is approximately 25-30 times more potent than hydrocortisone. In the Indian context, it is widely used for a broad spectrum of inflammatory, allergic, autoimmune, and neoplastic conditions, and gained significant public attention during the COVID-19 pandemic for its role in managing severe respiratory distress.
| Onset | Duration | Bioavailability |
|---|---|---|
| Variable: Immunosuppressive/anti-inflammatory effects begin within 1-2 hours of oral administration. Peak plasma concentrations occur in 1-2 hours. | Long-acting: Biological half-life is 36-54 hours. Duration of hypothalamic-pituitary-adrenal (HPA) axis suppression exceeds 48 hours. | Approximately 80% for oral tablet formulation. |
2. Mechanism of Action
Dexamethasone binds to intracellular glucocorticoid receptors (GRs) in the cytoplasm, forming a complex that translocates to the nucleus. This complex binds to Glucocorticoid Response Elements (GREs) on DNA, modulating gene transcription. It increases the synthesis of anti-inflammatory proteins (e.g., lipocortin-1) and decreases the synthesis of pro-inflammatory mediators (e.g., cytokines, chemokines, adhesion molecules, enzymes like COX-2). It also induces apoptosis of lymphocytes, particularly T-cells and eosinophils.
3. Indications & Uses
- Inflammatory conditions (e.g., rheumatoid arthritis, severe osteoarthritis flare)
- Allergic disorders (e.g., severe allergic rhinitis, contact dermatitis, drug reactions)
- Dermatological diseases (e.g., pemphigus vulgaris, severe psoriasis, exfoliative dermatitis)
- Respiratory diseases (e.g., bronchial asthma (acute exacerbation), COPD exacerbation, symptomatic sarcoidosis)
- Ophthalmic inflammation (posterior segment uveitis, optic neuritis)
- Cerebral edema (associated with primary or metastatic brain tumors, TBI)
- Endocrine disorders (e.g., congenital adrenal hyperplasia, adrenal insufficiency)
- Hematologic/Oncologic disorders (e.g., induction therapy in ALL, AML; antiemetic in chemotherapy; myeloma)
4. Dosage & Administration
Adult Dosage: Highly variable based on condition. Anti-inflammatory/immunosuppressive: 0.5mg to 9mg per day in divided doses. Cerebral edema: Initial loading dose of 10mg IV, then 4mg IM/IV every 6 hours, then tapered. Anti-emetic (chemotherapy): 8mg to 20mg IV before chemotherapy. Adrenal insufficiency: 0.5mg to 1mg daily. Always use the lowest effective dose for the shortest duration.
Administration: Oral: Take with food or milk to minimize GI upset. Do not crush or chew enteric-coated tablets. For once-daily dosing, take in the morning (around 8 AM) to mimic the body's natural cortisol rhythm and reduce HPA axis suppression. Do not stop abruptly after prolonged use (>2-3 weeks); must be tapered gradually.
5. Side Effects
Common side effects may include:
- Insomnia, nervousness, mood changes
- Increased appetite, weight gain (central obesity)
- Fluid retention, edema
- Dyspepsia, heartburn
- Hyperglycemia (especially in diabetics)
- Cushingoid habitus (moon face, buffalo hump)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin/Acenoocumarol | Dexamethasone may alter anticoagulant response (increase or decrease INR); monitor closely. | Major |
| Phenytoin, Phenobarbital, Carbamazepine, Rifampicin | Induce CYP3A4, increasing dexamethasone metabolism, reducing its efficacy. | Major |
| Ketoconazole, Itraconazole, Clarithromycin, Erythromycin | Inhibit CYP3A4, decreasing dexamethasone metabolism, increasing risk of toxicity. | Major |
| NSAIDs (e.g., Ibuprofen, Diclofenac) | Increased risk of GI ulceration and bleeding. | Major |
| Diuretics (e.g., Furosemide, Hydrochlorothiazide) | Enhanced potassium loss, leading to severe hypokalemia. | Major |
| Antidiabetics (Insulin, Metformin, Sulfonylureas) | Dexamethasone causes hyperglycemia, antagonizing their effect; dose adjustment needed. | Major |
| Live Vaccines (MMR, Varicella, OPV) | Risk of disseminated infection due to immunosuppression; avoid. | Contraindicated |
| Digoxin | Risk of digitalis toxicity due to hypokalemia. | Moderate |
7. Patient Counselling
- DO take the medicine exactly as prescribed by your doctor.
- DO take oral doses with food or milk.
- DO inform all your doctors and dentists that you are taking dexamethasone, especially before any surgery.
- DO carry a steroid alert card/bracelet.
- DON'T stop taking the medicine suddenly if you have been on it for more than 2-3 weeks.
- DON'T take live vaccines (e.g., MMR, chickenpox) without consulting your doctor.
- DON'T take over-the-counter NSAIDs (like ibuprofen) without asking your doctor.
8. Toxicology & Storage
Overdose: Acute overdose is unlikely to cause acute life-threatening toxicity but will manifest as signs of Cushing's syndrome: severe hypertension, hyperglycemia, fluid retention, psychosis, and electrolyte imbalances (hypokalemia, metabolic alkalosis). Chronic overdose leads to iatrogenic Cushing's syndrome.
Storage: Store in a cool, dry place, protected from light and moisture. Keep out of reach of children. Store at room temperature (15-25°C). Do not use after the expiry date printed on the pack.