Classification of Glucocorticoid Steroids by Potency and Duration of Action
Glucocorticoids are classified into three categories based on duration of action (short-, intermediate-, and long-acting) and by relative anti-inflammatory potency compared to hydrocortisone, with potency ranging from 1× (hydrocortisone) to 25× (dexamethasone). 1
Classification by Duration of Action
Short-Acting Glucocorticoids
- Hydrocortisone (cortisol): Biological half-life 8-12 hours
- Cortisone acetate: Requires hepatic conversion to hydrocortisone (active 11-β-hydroxyl form) to be effective 2
- These are the least potent systemic glucocorticoids 3
- Preferred as primary treatment option for replacement therapy 4
Intermediate-Acting Glucocorticoids
- Prednisone: Biological half-life 12-36 hours, reaches peak plasma levels in 4-6 hours 5, 6
- Prednisolone: Similar duration to prednisone
- Methylprednisolone: Similar duration to prednisone
- These are 4-5 times more potent than hydrocortisone 3
Long-Acting Glucocorticoids
- Dexamethasone: Biological half-life 36-72 hours
- Approximately 25 times more potent than hydrocortisone 3
- Has no mineralocorticoid activity (unlike hydrocortisone which has potent mineralocorticoid effects) 4
Physiologic Dose Equivalents
The following doses represent physiologic daily dose equivalents (equivalent to average daily cortisol production of 9-10 mg/day) 1:
- Hydrocortisone: 15-25 mg/day
- Prednisone or Prednisolone: 4-6 mg/day
- Methylprednisolone: 3-5 mg/day
- Dexamethasone: 0.25-0.5 mg/day
Any dose exceeding these equivalents is considered supraphysiologic therapy and carries increased risk for adverse effects and HPA axis suppression 1.
Clinical Implications by Potency
Risk Stratification
- Duration threshold for HPA axis suppression: ≥3-4 weeks of supraphysiologic doses 1, 7
- Mortality risk: Prednisone equivalent >5 mg/day associated with adjusted hazard ratio of 1.97 for all-cause mortality; no increased mortality observed with doses <5 mg/day 1
Important Caveats
- Plasma half-life does NOT correlate with duration of action or potency 2—the biological effects persist far longer than circulating levels
- Prednisone and cortisone are inactive prodrugs requiring hepatic conversion to prednisolone and hydrocortisone respectively; this conversion may be impaired in liver disease 2
- Duration of action varies with dose—higher doses produce longer-lasting effects 2
Mineralocorticoid Activity
- Hydrocortisone: Potent mineralocorticoid activity
- Prednisolone: Reduced mineralocorticoid activity
- Dexamethasone: No mineralocorticoid activity 4
This classification system is critical for selecting appropriate glucocorticoid therapy, predicting adverse effects, determining tapering schedules, and assessing risk for adrenal insufficiency upon discontinuation.