Hydrocortisone Onset of Action
Intravenous hydrocortisone demonstrates clinical effects within one hour, with peak plasma levels achieved at 10-20 minutes, while intramuscular administration reaches therapeutic levels within 11±5 minutes. 1, 2
Route-Specific Timing
Intravenous Administration
- Immediate bioavailability occurs with IV hydrocortisone, producing demonstrable clinical effects within one hour of administration. 1, 2
- Peak plasma cortisol levels are reached at 10-20 minutes following IV injection. 1
- The FDA label confirms that effects are evident within one hour and persist for a variable period, with nearly complete excretion within 12 hours. 2
- For sustained therapeutic effect, injections should be administered every 4-6 hours if constantly high blood levels are required. 2
Intramuscular Administration
- IM hydrocortisone is rapidly absorbed with therapeutic levels achieved within 11±5 minutes. 1
- The excretion pattern following IM administration is similar to IV injection. 1, 2
- Both IV and IM routes are preferred for emergency situations requiring rapid onset of action. 1
Clinical Context and Timing Considerations
Emergency Situations
- For adrenal crisis, the rapid onset of IV or IM hydrocortisone is critical, as delays in administration can be fatal. 1
- In septic shock, early initiation of hydrocortisone (within 3 hours) reduces time to vasopressor discontinuation compared to late initiation. 1, 3
Perioperative Management
- For surgical stress coverage, hydrocortisone 100mg IV is administered at induction, followed by continuous infusion (200mg/24 hours) to maintain therapeutic levels throughout the perioperative period. 1, 4
Important Limitation in Anaphylaxis
- Corticosteroids are NOT helpful for treating acute anaphylaxis due to their slow onset of anti-inflammatory action (4-6 hours), though they are given to prevent biphasic or protracted reactions. 1
- This 4-6 hour delay for anti-inflammatory effects contrasts with the more rapid hemodynamic effects seen in other conditions. 1
Pharmacokinetic Profile
Oral Administration
- Following oral hydrocortisone, peak serum cortisol concentrations are reached at approximately 1.2 hours (range: 0.3-3.3 hours). 5
- Oral bioavailability is high at 94.2% in the morning, with cortisol concentrations reaching supraphysiological levels within 1-2 hours after administration. 5
- Serum concentrations decline to undetectable levels 7-9 hours after oral administration. 5
Clinical Pearls
The distinction between hemodynamic effects (within 1 hour) and anti-inflammatory effects (4-6 hours) is clinically important when selecting hydrocortisone for specific indications. 1, 2
For conditions requiring immediate hemodynamic support (adrenal crisis, septic shock), the one-hour onset is clinically relevant, while for inflammatory conditions, the delayed anti-inflammatory action must be considered. 1