Dexamethasone

Active Ingredient & Mechanism of Action

• Active Ingredient: Dexamethasone.
• Mechanism: Dexamethasone crosses cell membranes to bind with intracellular glucocorticoid receptors. This complex translocates into the cell nucleus to:
  1. Inhibit Inflammatory Cascades: Suppress the transcription of pro-inflammatory cytokines, chemokines, and inflammatory enzymes (such as COX-2).
  2. Inhibit Immune Cell Activity: Reduce white blood cell recruitment, capillary permeability, and vasodilation at site-specific inflammation.
  3. Minimal Mineralocorticoid Effect: Unlike hydrocortisone or cortisone, dexamethasone produces virtually no sodium-retaining (mineralocorticoid) activity, making it less likely to cause direct electrolyte-driven fluid retention at lower standard doses.

Dosage Forms & Available Strengths

• Oral Tablets: Available in various strengths including 0.5 mg, 1 mg, 2 mg, 4 mg, and 6 mg tablets.
• Oral Liquid / Solution: 0.5 mg / 5 mL liquid formulations.
• Injectable Solution: 4 mg / mL and 10 mg / mL vials for intravenous (IV), intramuscular (IM), or intra-articular administration.
• Ophthalmic / Otic Formulations: Eye drops, eye ointments, and ear drops (often combined with antibiotics) for localized ocular or auditory inflammation.

Clinical Indications

• Severe Allergic Conditions: Acute severe asthma attacks, angioedema, serum sickness, drug hypersensitivity, and anaphylaxis (as adjunctive therapy).
• Autoimmune & Inflammatory Diseases: Severe flare-ups of rheumatoid arthritis, systemic lupus erythematosus (SLE), and inflammatory skin disorders (e.g., severe pemphigus, Stevens-Johnson syndrome support).
• Cerebral Edema: Reduction of brain swelling associated with primary or metastatic brain tumors, neurosurgery, or head trauma.
• Respiratory Illnesses: Croup (laryngotracheobronchitis) in pediatric patients and severe acute respiratory distress syndromes (including severe COVID-19 in hospitalized patients requiring oxygen).
• Oncology & Palliative Care: Management of chemotherapy-induced nausea and vomiting (CINV) and short-term appetite stimulation or pain relief in terminal cases.
• Diagnostic Tool: Dexamethasone Suppression Test (DST) used to evaluate Cushing’s syndrome and adrenal dysfunction.

Key Pharmacokinetics

• Absorption: Rapidly and well absorbed following oral administration.
• Metabolism: Metabolized in the liver primarily via the CYP3A4 enzyme system.
• Half-Life & Biological Duration: Plasma half-life is approximately 3 to 5 hours, but its biological/anti-inflammatory half-life is long (36 to 54 hours), allowing for once-daily or alternate-day dosing regimens.
• Elimination: Excreted primarily via urine as un-conjugated metabolites.

Administration Guidelines

• Food Requirement: Take oral tablets with or immediately after food or milk to minimize gastric irritation.
• Timing: When taken as a single daily dose, it is typically recommended in the morning to align with natural circadian cortisol production and reduce sleep disturbance/insomnia.
• Crucial Rule — Gradual Tapering: Extended courses (longer than 2 weeks) suppress the hypothalamic-pituitary-adrenal (HPA) axis. Stopping dexamethasone abruptly can trigger a severe, life-threatening adrenal crisis. Doses must be gradually tapered under medical supervision.

Safety Profile & Considerations

• Short-Term Side Effects: Increased appetite, weight gain, insomnia, restlessness/mood shifts, transient elevation in blood glucose, and mild stomach discomfort.
• Long-Term / High-Dose Risks:
  • Immunosuppression: Increased susceptibility to fungal, viral, or bacterial infections, and potential masking of infection signs.
  • Metabolic & Endocrine: Steroid-induced diabetes mellitus, Cushingoid features (“moon face”, central obesity), and adrenal suppression.
  • Musculoskeletal: Osteoporosis, muscle wasting (myopathy), and aseptic necrosis of bone heads.
  • Gastrointestinal: Gastric ulcers or GI bleeding, especially when taken with NSAIDs.
  • Ophthalmic: Glaucoma, elevated intraocular pressure, and posterior subcapsular cataracts.
• Pregnancy & Lactation: Crosses the placenta. Should only be used during pregnancy if the potential benefit justifies the risk to the fetus.
• Key Drug Interactions:
  • CYP3A4 Inducers (e.g., Carbamazepine, Phenytoin, Rifampicin): Accelerate dexamethasone metabolism, reducing its effectiveness.
  • CYP3A4 Inhibitors (e.g., Ketoconazole, Erythromycin): Increase dexamethasone blood levels and side effect risks.
  • NSAIDs & Aspirin: Concomitant use significantly elevates gastrointestinal ulceration and bleeding risks.
  • Antidiabetics: Dexamethasone raises blood glucose, necessitating dose adjustments of insulin or oral antidiabetic agents.

Note: Dexamethasone is a potent, high-strength prescription corticosteroid. Dosing protocols, duration of use, and tapering schedules must be strictly monitored by a licensed healthcare professional.