Best Muscle for Hydrocortisone Injection in Adrenal Insufficiency
When intramuscular hydrocortisone is required in adrenal crisis or emergency situations, any large muscle group is acceptable—the deltoid, vastus lateralis (thigh), or gluteal muscles can all be used, with the key priority being rapid administration without delay rather than the specific muscle chosen. 1
Route Selection Priority
The guidelines emphasize that route of administration matters more than the specific muscle site:
- Intravenous administration is strongly preferred when available, as continuous IV infusion of hydrocortisone 200 mg/24 hours maintains cortisol concentrations in the physiologic stress range more effectively than intermittent bolus dosing 1, 2
- Intramuscular injection should be used immediately if IV access cannot be established quickly—do not delay treatment attempting to secure IV access 1, 3
- The guideline explicitly states "intramuscular administration may be prescribed in circumstances where i.v. infusion therapy is impractical" 1
Emergency Dosing Regardless of Muscle Site
For acute adrenal crisis or severe stress:
- Hydrocortisone 100 mg should be given immediately by IV or IM route 1, 4
- This is followed by either continuous IV infusion of 200 mg/24 hours OR hydrocortisone 50 mg IM every 6 hours 1
- In labor and delivery specifically, the regimen is hydrocortisone 100 mg IM followed by 50 mg every 6 hours IM as an alternative to IV infusion 1
Practical Muscle Selection Considerations
While guidelines do not mandate a specific muscle, standard clinical practice suggests:
- Deltoid muscle: Accessible and commonly used for emergency injections, appropriate for volumes up to 2 mL
- Vastus lateralis (anterolateral thigh): Preferred in children and when larger volumes are needed 1
- Gluteal muscles: Traditional site but requires proper positioning
Critical Safety Points
- Never delay hydrocortisone administration to debate injection site—adrenal crisis is life-threatening and requires immediate treatment 1, 4, 3
- All patients with adrenal insufficiency should have emergency injectable hydrocortisone at home and receive self-injection training 4, 3
- Patients should wear medical alert bracelets to trigger stress-dose corticosteroids by emergency medical services 1, 4
Common Pitfall to Avoid
The most dangerous error is delaying treatment while attempting to establish IV access or debating the optimal injection site. The guidelines consistently emphasize that if peripheral venous access cannot be achieved quickly, intramuscular administration should be performed without delay 3. The pharmacokinetic study demonstrated that while continuous IV infusion is superior for maintaining steady cortisol levels, IM bolus administration still achieves adequate cortisol concentrations during the critical initial period 2.