Corticosteroids in Medicine
Corticosteroids are among the most potent anti-inflammatory and immunosuppressive drugs available. Their broad effects on nearly every organ system demand careful dosing, monitoring, and tapering.
## Mechanism of Action
Corticosteroids bind intracellular glucocorticoid receptors, forming complexes that translocate to the nucleus and modulate gene transcription. They suppress multiple inflammatory pathways simultaneously:
- **Transrepression** -- Inhibit NF-kappaB and AP-1 transcription factors, reducing production of cytokines (IL-1, IL-6, TNF-alpha), chemokines, and adhesion molecules.
- **Transactivation** -- Upregulate anti-inflammatory proteins like lipocortin-1 (inhibits phospholipase A2, blocking arachidonic acid release).
- **Immune cell effects** -- Reduce circulating lymphocytes, eosinophils, and monocytes while increasing neutrophil counts (demargination).
## Potency Comparison
| Agent | Anti-inflammatory Potency | Mineralocorticoid Effect | Half-Life |
|-------|--------------------------|-------------------------|-----------|
| Hydrocortisone | 1 (reference) | High | 8-12 h |
| Prednisone | 4 | Moderate | 12-36 h |
| Methylprednisolone | 5 | Low | 12-36 h |
| Dexamethasone | 25-30 | Minimal | 36-72 h |
Prednisone is a prodrug converted to prednisolone in the liver. In severe liver disease, prednisolone may be preferred directly.
## Clinical Uses
- **Inflammatory diseases** -- Rheumatoid arthritis, SLE, IBD, vasculitis (often as bridge therapy while slower-acting DMARDs take effect).
- **Allergic reactions** -- Anaphylaxis (adjunct to epinephrine), severe asthma exacerbations, allergic rhinitis (intranasal).
- **Respiratory** -- COPD exacerbations, COVID-19 hypoxia (dexamethasone reduced mortality in RECOVERY trial).
- **Autoimmune** -- Multiple sclerosis relapses (IV methylprednisolone), autoimmune hepatitis.
- **Oncology** -- Lymphoma protocols, cerebral edema from brain metastases, antiemesis.
- **Adrenal insufficiency** -- Physiologic replacement (hydrocortisone) for Addison's disease.
## Long-Term Adverse Effects
Chronic systemic corticosteroids affect virtually every organ system:
- **Metabolic** -- Hyperglycemia (steroid diabetes), weight gain, dyslipidemia, Cushingoid features.
- **Musculoskeletal** -- Osteoporosis (start calcium, vitamin D, and consider bisphosphonate early), avascular necrosis, myopathy.
- **Infectious** -- Immunosuppression increases risk of opportunistic infections, reactivation of latent TB and hepatitis B.
- **Psychiatric** -- Insomnia, mood swings, psychosis (steroid psychosis), cognitive impairment.
- **Ophthalmologic** -- Posterior subcapsular cataracts, increased intraocular pressure.
- **Dermatologic** -- Skin thinning, easy bruising, poor wound healing.
- **Adrenal suppression** -- HPA axis suppression after >2-3 weeks of use; abrupt cessation causes adrenal crisis.
## Tapering Principles
Gradual dose reduction is mandatory after prolonged use (>2-3 weeks) to allow HPA axis recovery. Typical approach: reduce by 10-20% every 1-2 weeks. Stress doses may be needed during illness or surgery for up to a year after discontinuation.
## Key Takeaways
- Corticosteroids are powerful but carry cumulative toxicity -- use the lowest dose for the shortest duration.
- Always plan an exit strategy (taper schedule, steroid-sparing agent transition) when starting systemic steroids.
- Bone protection should begin at initiation if therapy is expected to exceed 3 months.
- Never stop chronic corticosteroids abruptly -- adrenal crisis can be fatal.