Stanozolol
**Stanozolol** is a synthetic **anabolic-androgenic steroid (AAS)** derived from testosterone. Historically, it was widely used in veterinary medicine to improve appetite, promote weight gain, increase strength and vitality, and treat anemia associated with chronic disease. While FDA-approved commercial products (such as Winstrolยฎ-V) are no longer marketed in the USA, the drug remains available through veterinary compounding pharmacies. > **Clinical Pearl:** Stanozolol has a notoriously high incidence of **hepatotoxicity in cats**. Its use in feline patients is highly discouraged unless absolutely necessary, and requires extreme caution and rigorous monitoring. Though it possesses a higher anabolic-to-androgenic ratio compared to endogenous testosterone, androgenic side effects (such as behavioral changes and reproductive suppression) can still occur, particularly with prolonged use or high doses. It is a **controlled substance** due to its potential for human abuse.
Mechanism: Stanozolol is highly lipophilic and diffuses across the cell membrane to bind with intracellular **androgen receptors**. * **Anabolic Pathway:** The receptor-hormone complex translocates to the nucleus โ binds to specific DNA sequences (hormone response elements) โ modulates transcription of target genes โ increases **protein synthesis** (anabolism), promotes a positive nitrogen balance, and induces muscle hypertrophy. * **Erythropoietic Pathway:** Stimulates the production of **erythropoietin** in the kidneys โ stimulates bone marrow โ increases red blood cell production (useful in treating anemia of chronic disease). * **Fibrinolytic Pathway:** Enhances fibrinolysis after parenteral injection, which provides a theoretical basis for its use in treating feline aortic thromboembolism or thrombosis in nephrotic syndrome.
Dosing by species
- For acute or subacute aflatoxicosis in ruminants ยท Stanozolol 2 mg/kg IM (plus activated charcoal 6.7 mg/kg as a 30% w/v slurry in M/15, pH 7 phosphate buffer). ยท IM ยท Single dose ยท Do not combine with oxytetracycline therapy.
- For acute or subacute aflatoxicosis in ruminants ยท Stanozolol 2 mg/kg IM (plus activated charcoal 6.7 mg/kg as a 30% w/v slurry in M/15, pH 7 phosphate buffer). ยท IM ยท Single dose ยท Do not combine with oxytetracycline therapy.
- As an anabolic agent per labeled indications ยท 1-2 mg PO twice daily; or 25 mg deep IM, may repeat weekly. ยท PO/IM ยท q12h (PO) or weekly (IM) ยท Several weeks, depending on response ยท EXTREME CAUTION: High incidence of hepatotoxicity in cats.
- General therapeutics ยท 0.5 mg/kg PO or SC twice daily ยท PO/SC ยท q12h ยท Use with caution in hepatic disease.
- As an anabolic agent per labeled indications ยท 0.55 mg/kg (25 mg per 100 pounds of body weight) IM deeply. May repeat weekly for up to and including 4 weeks. ยท IM ยท weekly ยท Up to 4 weeks ยท ARCI UCGFS Class 4 Drug. Contraindicated in breeding stallions and food animals.
- As an anabolic agent to promote weight gain and recovery from disease ยท 0.5-1 mL/kg (25-50 mg/kg) IM once or twice weekly. ยท IM ยท Once or twice weekly ยท Use with caution in birds with renal disease.
Routes of administration
Contraindications
- Pregnant animals (Category X - teratogenic)
- Breeding stallions
- Food-producing animals
- Patients with hepatic dysfunction
- Patients with hypercalcemia
- Patients with a history of myocardial infarction
- Patients with pituitary insufficiency
- Patients with prostate carcinoma or benign prostatic hypertrophy
- Patients with mammary carcinoma
- During the nephrotic stage of nephritis
Adverse effects
- Hepatotoxicity (especially high incidence in cats)
- Sodium, calcium, potassium, water, chloride, and phosphate retention
- Behavioral changes (androgenic effects such as increased aggression)
- Reproductive abnormalities (oligospermia, estrus suppression)
- Mild androgenic effects (usually only at high doses or prolonged use)
Drug interactions
- Anticoagulants (heparin, warfarin) ยท Anabolic agents may potentiate the effects of anticoagulants; monitoring of INR/PT and dosage adjustment of the anticoagulant are recommended.
- Corticosteroids ยท Anabolics may enhance the edema that can be associated with ACTH or adrenal steroid therapy.
- Insulin ยท Anabolics may decrease blood glucose and decrease insulin requirements; diabetic patients receiving insulin may need dosage adjustments.
Monitoring
- Androgenic side effects (behavioral changes)
- Fluid and electrolyte status (especially in cardiac/renal patients)
- Liver function tests (crucial in cats)
- RBC count and indices (if treating anemia)
- Weight and appetite
Overdose
No specific information was located for this agent in veterinary species. In humans, **sodium and water retention** can occur after overdosage of anabolic steroids. **Treatment:** Treat supportively and monitor liver function should an inadvertent overdose be administered.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.