Corticotropin (ACTH)
Adrenocorticotropic hormone
Also known as: Adrenomone · H.P. Acthar Gel · Adrenocorticotropic hormone · Adrenocorticotrophin · Corticotropinum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| ACTH Stimulation Test | 2.2 Units/kg IM | IM | Once | — | 🌎 NA |
| ACTH Stimulation Test | 0.5 Units/kg IM | IM | Once | — | 🌎 NA |
- ACTH Stimulation Test: Draw baseline blood sample, administer gel, then draw second sample 120 minutes after injection.
- ACTH Stimulation Test: Draw baseline blood sample, administer gel, then draw second sample 120 minutes after injection.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| ACTH Stimulation Test | 2.2 Units/kg IM | IM | Once | — | 🌎 NA |
| ACTH Stimulation Test | 0.5 Units/kg IM | IM | Once | — | 🌎 NA |
- ACTH Stimulation Test: Draw baseline blood sample, administer gel, then draw samples at 60 minutes and 120 minutes after injection.
- ACTH Stimulation Test: Draw baseline blood sample, administer gel, then draw sample 120 minutes after injection.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| ACTH Stimulation Test | 16-25 Units IM | IM | Once | — | 🌎 NA |
- ACTH Stimulation Test: Draw baseline blood sample for corticosterone (not cortisol), administer IM, draw second sample 1-2 hours later.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| ACTH Stimulation Test | 1 Unit/kg IM | IM | Once | — | 🌎 NA |
| ACTH Stimulation Test | 1 Unit/kg IM | IM | Once | — | 🌎 NA |
- ACTH Stimulation Test: Draw baseline blood sample, administer gel, then draw second sample 8 hours later.
- ACTH Stimulation Test: Administer between 8 and 10 AM; take post ACTH cortisol levels at 2 and 4 hours post dose.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| ACTH deficiency or primary bovine ketosis | 200-600 Units initially followed by daily or semi-daily dose of 200-300 Units | IM | daily or semi-daily | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Corticotropin (ACTH) is a 39-amino acid polypeptide hormone secreted by the anterior pituitary. In veterinary medicine, it is used primarily as a diagnostic agent to evaluate adrenal gland function.
- Primary Use: The ACTH stimulation test is used to diagnose hypoadrenocorticism (Addison's disease), identify iatrogenic hyperadrenocorticism (Cushing's syndrome), and monitor the efficacy of adrenal-suppressive therapies (e.g., mitotane or trilostane).
- Limitations: It is considered relatively insensitive as a screening test for naturally occurring hyperadrenocorticism in dogs compared to the low-dose dexamethasone suppression test (LDDST).
- Clinical Pearl: Due to the high cost, limited availability, and variable potency of natural porcine ACTH gel products, synthetic cosyntropin is now the preferred agent for ACTH stimulation testing in modern clinical practice.
Mechanism of action
Endogenous ACTH release is controlled by corticotropin-releasing factor (CRF) from the hypothalamus and is subject to negative feedback by glucocorticoids.
Exogenous corticotropin binds to melanocortin-2 receptors (MC2R) in the zona fasciculata of the adrenal cortex $\rightarrow$ stimulates the conversion of cholesterol to pregnenolone via cholesterol desmolase $\rightarrow$ rapidly increases the synthesis and release of glucocorticoids (primarily cortisol in mammals and corticosterone in birds and reptiles).
Safety & warnings
Contraindications
- Hypersensitivity to porcine proteins
- Intravenous (IV) administration of the repository gel formulation
Adverse effects
- Fluid and electrolyte disturbances (with prolonged/chronic use)
- Hypersensitivity reactions (rare)
Precautions
Do not administer the repository gel form intravenously (IV). Use cautiously during pregnancy (FDA Category C); it may be embryocidal, and benefits must outweigh risks. If used chronically (rare in veterinary medicine), potassium supplementation may be required.
Drug interactions
May antagonize effects in patients with myasthenia gravis
May increase electrolyte loss (e.g., hypokalemia) if used chronically
Exogenous administration on the day of the test will cross-react with cortisol assays and invalidate test results
Monitoring
- Serum cortisol levels (pre- and post-injection for mammals)
- Serum corticosterone levels (pre- and post-injection for birds/reptiles)
- Electrolytes and fluid balance (only if used chronically)
Pharmacokinetics
Half-life
Absorption
Rapidly degraded by proteolytic enzymes in the gut, so it cannot be given PO. After IM injection, the repository gel is absorbed slowly over 8-16 hours.
Distribution
Circulates in plasma.
Metabolism
Rapidly degraded by proteolytic enzymes.
Elimination
Rapidly cleared from circulation. Despite a short circulating half-life, the slow absorption of the gel formulation allows effects to persist for up to 24 hours.
Overdose
When used for diagnostic purposes, acute inadvertent overdoses are highly unlikely to cause any significant adverse effects. Monitor the patient as required and treat symptomatically if necessary.
Available products
Formulations
- Repository injection (gel)
- Injection (aqueous)
Human-labeled
- Corticotropin Repository Injection: 80 Units/mL in 5 mL multi-dose vials (H.P. Acthar Gel)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Corticotropin for injection (aqueous) can be stored at room temperature (15-30°C) before reconstitution; after reconstitution, refrigerate and use within 24 hours. Repository corticotropin injection (gel) should be stored in the refrigerator (2-8°C). To allow ease in withdrawing the thick gel into a syringe, the vial may be warmed with warm water prior to use.
Client information
Your veterinarian is using this medication to perform an ACTH stimulation test, which evaluates how well your pet's adrenal glands are functioning.
- The Procedure: The test involves drawing a baseline blood sample, giving an injection of the hormone, and then drawing another blood sample 1 to 2 hours later (or longer in horses).
- Safety: > Note: This is a very safe diagnostic test. Side effects from a single dose are extremely rare.
- Preparation: Ensure your veterinarian knows about all medications your pet is taking, especially any steroid medications (like hydrocortisone creams or pills), as these can interfere with the test results.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.