Prednisolone vs Dexamethasone
Clinical Comparison
Clinical Context
Prednisolone is the workhorse oral glucocorticoid in UK general practice and hospital medicine. Dexamethasone is reserved for situations requiring high potency with no mineralocorticoid effect (cerebral oedema, croup, anti-emesis) or where its long duration is advantageous.
Drug Profiles
Prednisolone
Glucocorticoid (intermediate-acting)
Mechanism
Binds to intracellular glucocorticoid receptors, translocates to nucleus, upregulates anti-inflammatory genes and suppresses pro-inflammatory cytokine transcription
Indications
- Acute asthma exacerbation
- COPD exacerbation
- Inflammatory bowel disease
- Autoimmune conditions
- Allergic reactions
- Nephrotic syndrome
Common Doses
Acute asthma: 40-50 mg OD for 5 days; Maintenance: 5-15 mg OD; Varies widely by indication
Route
Oral (tabs and soluble), rectal
Onset & Duration
Onset 1-2 hours; biological half-life 12-36 hours
Dexamethasone
Glucocorticoid (long-acting, high potency)
Mechanism
Same as prednisolone but with 6-7x greater glucocorticoid potency and negligible mineralocorticoid activity
Indications
- Cerebral oedema (brain tumours)
- Croup (viral laryngotracheobronchitis)
- Bacterial meningitis (adjunctive)
- Anti-emetic (chemotherapy-induced)
- COVID-19 (hospitalised, requiring oxygen)
- Preterm labour (fetal lung maturation)
Common Doses
Cerebral oedema: 8-16 mg/day; Croup: 0.15-0.6 mg/kg single dose; COVID-19: 6 mg OD for 10 days; Anti-emetic: 4-8 mg
Route
Oral, IV, IM
Onset & Duration
Onset 1-2 hours oral; biological half-life 36-54 hours
Key Differences
| Category | Prednisolone | Dexamethasone |
|---|---|---|
| Potency (glucocorticoid) | 4x cortisol (moderate) | 25-30x cortisol (very high) — roughly 6-7x prednisolone |
| Mineralocorticoid effect | Moderate — some sodium retention | Negligible — no sodium/water retention |
| Duration of action | Intermediate (12-36 hours) | Long-acting (36-54 hours) |
| Typical use | Standard for most inflammatory and autoimmune conditions | Cerebral oedema, croup, anti-emetic, COVID-19 |
| Equivalent doses | 5 mg prednisolone | 0.75 mg dexamethasone |
| Formulations | Oral tablets and soluble | Oral, IV, and IM |
Potency (glucocorticoid)
4x cortisol (moderate)
25-30x cortisol (very high) — roughly 6-7x prednisolone
Mineralocorticoid effect
Moderate — some sodium retention
Negligible — no sodium/water retention
Duration of action
Intermediate (12-36 hours)
Long-acting (36-54 hours)
Typical use
Standard for most inflammatory and autoimmune conditions
Cerebral oedema, croup, anti-emetic, COVID-19
Equivalent doses
5 mg prednisolone
0.75 mg dexamethasone
Formulations
Oral tablets and soluble
Oral, IV, and IM
Key Advantages
Prednisolone
- Standard oral glucocorticoid in UK practice
- Moderate potency with manageable mineralocorticoid effects
- Available as soluble tablets for children
- Extensive evidence across all inflammatory conditions
- Cheap and widely available
Dexamethasone
- Very potent — lower doses needed
- No mineralocorticoid effect — no sodium/water retention
- Long duration allows less frequent dosing
- Proven mortality benefit in COVID-19 (RECOVERY trial)
- IV formulation for acute situations
Key Cautions
Prednisolone
- Adrenal suppression with prolonged use (>3 weeks needs taper)
- Hyperglycaemia — may unmask or worsen diabetes
- Osteoporosis with chronic use (co-prescribe bone protection)
- Immunosuppression — risk of infection
- GI ulceration — caution with NSAIDs
- Psychiatric effects (insomnia, mania, psychosis at high doses)
Dexamethasone
- Very potent — adrenal suppression even with short courses
- Higher risk of hyperglycaemia per unit of anti-inflammatory effect
- Same class risks as prednisolone but at lower doses
- Not typically used for general inflammatory conditions (too potent)
- Must taper carefully after prolonged use
Clinical Verdict
Use prednisolone as the standard oral steroid for most inflammatory conditions (asthma, COPD, IBD, autoimmune). Reserve dexamethasone for cerebral oedema, croup, anti-emesis, and situations where mineralocorticoid activity must be avoided.
Medical Disclaimer: This comparison is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare professional before making prescribing decisions. Verify all drug information with current clinical guidelines (BNF, NICE, SmPCs).
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