Purified Cortrophin Gel Dosing and Administration
Purified Cortrophin Gel (repository corticotropin injection) is administered at 80 USP units intramuscularly or subcutaneously, with the FDA-approved formulation available as 80 units/mL in multiple-dose vials or 40-80 unit prefilled syringes for subcutaneous use only. 1
Standard Dosing
The FDA-labeled product contains:
- Multiple-dose vials: 80 USP units/mL (for IM or SC use)
- Single-dose prefilled syringes: 40 USP units/0.5 mL or 80 USP units/mL (SC use only) 1
Administration Route and Technique
Intramuscular or subcutaneous injection is the approved route. The prefilled syringe formulation (SelfJect™) is specifically designed for subcutaneous delivery only and should be removed from refrigeration 45 minutes prior to injection 1.
For pediatric patients, while the device is appropriate for children over 2 years of age, an adult should administer the injection due to the force required to remove the protective cap and deliver the full dose 2.
Pharmacodynamic Profile
Following an 80-unit IM injection, peak cortisol concentration occurs at a median of 8 hours (range 3-12 hours), with baseline-corrected mean maximum cortisol levels of 34.52 µg/dL 1. This differs substantially from synthetic ACTH preparations—RCI induces approximately 5-fold lower free cortisol exposure compared to synthetic ACTH1-24 depot, despite higher plasma ACTH concentrations 3.
Clinical Context: Not a Replacement Therapy
Critical distinction: The evidence provided focuses on hydrocortisone for adrenal insufficiency replacement therapy (15-25 mg/day for primary AI, 10-20 mg/day for secondary AI in adults) 4. Purified Cortrophin Gel is not used for routine adrenal insufficiency replacement—it's a diagnostic and therapeutic agent for specific inflammatory conditions.
The French consensus guidelines recommend hydrocortisone as first-line treatment for adrenal insufficiency, with dosing split into 2-3 daily administrations 4. In acute adrenal crisis, treatment requires parenteral hydrocortisone hemisuccinate at 100 mg IM/IV, not corticotropin 4.
Key Administration Considerations
- Storage: Refrigerated; warm to room temperature before injection 1
- Injection sites: Standard IM or SC sites appropriate for the formulation used
- Frequency: Varies by indication (e.g., twice weekly dosing studied in clinical trials) 3
- Pediatric use: Appropriate for children >2 years; adult administration recommended 2
Safety Profile
Common adverse events include asthenic conditions, fluid retention, insomnia, headache, and increased blood glucose 2. The risk of hyperglycemia is notably lower than with high-dose corticosteroids—in diabetic MS patients, only 2 of 13 patients experienced elevated glucose with Cortrophin Gel versus 7 of 8 with prior steroid treatment 5.
The needle guard on prefilled syringes mitigates needlestick injury risk 2.
Important Caveat
Do not confuse diagnostic ACTH stimulation testing with therapeutic Cortrophin Gel use. The 250 µg cosyntropin test for diagnosing adrenal insufficiency 6 is entirely different from the 80-unit therapeutic dosing of repository corticotropin injection for inflammatory conditions.