Stanozolol — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	IM	1-5 mg/kg	Weekly	Duration: 4-8 weeks Notes: Use with caution in dogs with hepatic disease; monitor liver enzymes.
Dog	PO	0.5-2 mg/kg	q12h	Duration: 4-8 weeks Notes: Oral bioavailability is low; may require higher doses.
Cat	IM	1-5 mg/kg	Weekly	Duration: 4-8 weeks Notes: Use with caution in cats with hepatic disease; monitor liver enzymes.
Cat	PO	0.5-2 mg/kg	q12h	Duration: 4-8 weeks Notes: Oral bioavailability is low; may require higher doses.
Horse	IM	0.5-1 mg/kg	Weekly	Duration: 4-8 weeks Notes: Banned in competition; check withdrawal times for racing.
Horse	PO	0.1-0.2 mg/kg	q24h	Duration: 4-8 weeks Notes: Oral form may be less effective; monitor for hepatotoxicity.
Cattle	IM	0.5-1 mg/kg	Weekly	Duration: 4-8 weeks Notes: Not approved for food animals; extra-label use prohibited in the US.

Clinical Indications & Species Uses

General Indications

Anabolic support in chronic wasting conditions
Improve appetite and weight gain
Adjunct therapy for anemia

Dog (Canine)

Anabolic support for chronic wasting conditions
Improve appetite and weight gain in debilitated animals
Adjunct therapy for anemia (stimulates erythropoiesis)
Supportive care for chronic renal failure (to improve nitrogen balance)

Cat (Feline)

Anabolic support for chronic wasting conditions
Improve appetite and weight gain in debilitated animals
Adjunct therapy for anemia (stimulates erythropoiesis)

Horse (Equine)

Improve muscle mass and performance in racehorses (though banned in competition)
Supportive therapy for chronic respiratory disease (e.g., COPD) to improve appetite and condition
Adjunct therapy for anemia

Cattle (Bovine)

Promote growth and feed efficiency in beef cattle (though use is restricted in food animals)
Supportive therapy for chronic debilitating conditions

Pharmacology & Mechanism of Action

Drug Class: Anabolic steroid | Pharmacological Group: Androgen/anabolic steroid (synthetic derivative of testosterone)

Mechanism of Action: Stanozolol is a synthetic anabolic steroid derived from testosterone, with a modified structure that enhances anabolic activity while reducing androgenic effects. It binds to androgen receptors in target tissues, leading to increased protein synthesis, nitrogen retention, and muscle growth. It also stimulates erythropoietin production, increasing red blood cell mass, and may have anticatabolic effects by reducing glucocorticoid receptor binding and protein breakdown. In veterinary medicine, it is used to promote weight gain, improve appetite, and support recovery from chronic debilitating conditions.

Pharmacodynamics: Stanozolol exerts anabolic effects by promoting positive nitrogen balance, increasing muscle mass, and enhancing bone density. It also stimulates erythropoiesis, leading to increased hematocrit and hemoglobin. It may have immunomodulatory effects, including enhancement of complement activity and macrophage function. In horses, it has been shown to improve feed efficiency and exercise tolerance. Its androgenic effects are less pronounced than testosterone, but can still cause virilization in females and aggressive behavior in some animals.

⚡ Pharmacokinetics Summary

Absorption: Stanozolol is well absorbed after oral administration, but undergoes extensive first-pass metabolism in the liver, reducing bioavailability. Injectable formulations (IM or SC) provide more predictable absorption and higher systemic exposure.

Distribution: Stanozolol is widely distributed throughout the body, with high affinity for muscle and bone tissue. It crosses the blood-brain barrier to a limited extent. It is highly protein-bound in plasma (approximately 90-95%), primarily to albumin and sex hormone-binding globulin.

Metabolism: Stanozolol is extensively metabolized in the liver via oxidation, reduction, and conjugation. Major metabolites include 3'-hydroxystanozolol and 4β-hydroxystanozolol, which are excreted in urine and feces. The metabolism is species-dependent, with horses and cattle showing different metabolite profiles.

Excretion: Stanozolol and its metabolites are excreted primarily in urine (about 60%) and feces (about 40%). In cattle, the elimination half-life is relatively short, but in horses, it can be prolonged due to enterohepatic recirculation.

Half-Life: Dog: 2-4 hours; Horse: 8-12 hours; Cattle: 4-6 hours (approximate values)

Bioavailability: Oral: low (approximately 20-30% due to first-pass metabolism); IM: high (nearly 100%)

Protein Binding: Approximately 90-95% bound to plasma proteins (albumin and SHBG).

Available Formulations & Strengths

Oral Tablet 2 mg, 4 mg, 8 mg (PO)

Injectable Solution 50 mg/mL (IM)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to stanozolol or any component
Pregnancy (may cause virilization of female fetus)
Lactation (may pass into milk and affect offspring)
Prostatic carcinoma or other androgen-dependent neoplasia
Severe hepatic disease (may exacerbate liver damage)
Nephrotic syndrome or hypercalcemia (may worsen fluid retention and calcium imbalance)

Warnings & Clinical Precautions:

Use with caution in animals with cardiac, renal, or hepatic disease
May cause sodium and water retention, leading to edema
May cause hypercalcemia in some animals
May cause aggressive behavior or increased libido
In food animals, extra-label use is prohibited in the US; withdrawal times must be observed if used in other countries
In performance animals, stanozolol is banned by most equine and canine athletic associations
Monitor liver enzymes and renal function during therapy
Use with caution in growing animals as premature epiphyseal closure may occur

Adverse Effects & Reactions

Common:

Increased aggression
Increased libido
Sodium and water retention (edema)
Mild hepatotoxicity (elevated liver enzymes)
Acne or oily skin

Serious / Severe:

Hepatocellular damage (cholestatic jaundice)
Hypercalcemia
Cardiac hypertrophy
Premature epiphyseal closure in young animals
Virilization in females (clitoral enlargement, deepening voice)

Rare:

Peliosis hepatis (blood-filled cysts in liver)
Hepatic neoplasia (with prolonged use)
Behavioral changes (extreme aggression)
Bone marrow suppression (with high doses)

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Corticosteroids	Additive fluid retention and increased risk of hyperglycemia	Moderate
Anticoagulants (e.g., warfarin)	Increased risk of bleeding due to enhanced anticoagulant effect	High
Insulin or oral hypoglycemics	May alter blood glucose levels; monitor glucose	Moderate
Hepatotoxic drugs (e.g., ketoconazole, NSAIDs)	Increased risk of hepatotoxicity	High
Thyroid hormones	May increase thyroid hormone levels; monitor thyroid function	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Severe fluid retention (edema, ascites)
Hepatotoxicity (jaundice, elevated liver enzymes)
Hypercalcemia (weakness, depression, cardiac arrhythmias)
Aggression or behavioral changes
Premature epiphyseal closure in young animals

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Discontinue the drug immediately. Manage fluid retention with diuretics (e.g., furosemide) if severe. Monitor liver function and provide supportive care (e.g., hepatoprotectants like SAMe or silymarin). For hypercalcemia, administer fluids and consider calcitonin or bisphosphonates if severe. In cases of severe aggression, use sedatives if necessary. There is no specific antidote.

Food Animal Withdrawal Times

🥩 Meat: 30 days🥛 Milk: 7 days

Stanozolol is not approved for use in food animals in the US; extra-label use is prohibited. In other countries, withdrawal times may vary; consult local regulations. For horses intended for human consumption, withdrawal times must be observed.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature (20-25°C, excursions permitted to 15-30°C)

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light and moisture. Keep in tightly closed container. Do not freeze injectable solutions.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for veterinary use in dogs and horses (e.g., Winstrol-V) but not for food animals. Availability may vary by country.

Extra-Label (Off-Label) Use: In the US, stanozolol is not approved for veterinary use in food animals; extra-label use in food animals is prohibited by AMDUCA. In companion animals, extra-label use is permitted under AMDUCA with a valid VCPR. In performance animals, stanozolol is banned by most equine and canine athletic associations.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Stanozolol is used as an anabolic agent to improve appetite, promote weight gain, and support recovery in debilitated animals. It is particularly useful in chronic wasting conditions such as renal failure, chronic infections, and malnutrition. However, its use is controversial due to potential adverse effects and regulatory restrictions. In performance animals, it is banned, and its use can lead to disqualification. In food animals, it is prohibited in the US. Clinicians should weigh the benefits against the risks, especially in animals with hepatic or cardiac disease. Regular monitoring of liver enzymes, renal function, and electrolytes is recommended. Alternative anabolic agents (e.g., nandrolone) may be considered, but they have similar risks. Always adhere to local regulations and withdrawal times.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)