WINSTROL

Clinical safety rating: caution

Comprehensive clinical and safety monograph for WINSTROL (WINSTROL).

How it works

Winstrol (stanozolol) is an anabolic steroid derived from dihydrotestosterone. It binds to androgen receptors, increasing protein synthesis and inhibiting catabolic glucocorticoid activity, leading to enhanced muscle growth and reduced inflammation.

What the body does with it

Metabolism	Hepatic; primarily via reduction and conjugation, metabolized by enzymes such as 3α-hydroxysteroid dehydrogenase and glucuronosyltransferases.
Excretion	Primarily renal: 90% as metabolites (glucuronide and sulfate conjugates) and 10% as unchanged drug; minor biliary/fecal elimination (<5%).
Half-life	Terminal elimination half-life: 9-10 hours for oral administration (stanozolol); parenteral (IM) half-life extends to ~24 hours due to slow release from injection site. Clinical context: supports once-daily oral dosing or weekly IM dosing.
Protein binding	Approximately 94% bound to serum albumin and sex hormone-binding globulin (SHBG).
Volume of Distribution	Apparent Vd: ~0.3 L/kg (range 0.2-0.4 L/kg) for oral; reflects moderate distribution into extravascular tissues, with preferential binding to muscle and androgen receptors.
Bioavailability	Oral: ~3% due to extensive first-pass metabolism (stanozolol is 17α-alkylated, reducing bioavailability). Intramuscular: 100% bioavailable (parent compound released from injection site).
Onset of Action	Oral: 1-3 hours for initial effects (e.g., increased protein synthesis). Intramuscular: 2-4 hours; peak plasma concentrations at 24-48 hours post IM.
Duration of Action	Oral: 6-8 hours for single dose; with chronic dosing, effects (anabolic, androgenic) persist for several days. IM (aqueous suspension): duration of 2-3 weeks due to slow absorption; clinical effect lasts for 1-2 weeks after last dose.

Classification & Brands

Dosing & administration

Adults: 2 mg orally three times daily, or 50 mg/mL intramuscularly once monthly (3-4 week intervals) for anabolic effect. Dose range: 1-3 mg/kg/day for hereditary angioedema.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild to moderate renal impairment. For severe impairment (GFR <30 mL/min), use with caution; limited data suggest no dose adjustment but monitor fluid balance due to potential sodium and water retention.
Liver impairment	Contraindicated in severe hepatic disease. In Child-Pugh class A (mild), use with caution; no specific dose adjustment. In Child-Pugh class B or C (moderate to severe), avoid use due to risk of hepatotoxicity.
Pediatric use	Weight-based: 0.05-0.2 mg/kg/day orally for anabolic effect. For hereditary angioedema, 2-4 mg/day in children aged 6-12 years. Parenteral dose: 0.5-1 mg/kg intramuscularly once monthly. Not recommended in prepubertal children due to potential premature epiphyseal closure.
Geriatric use	No specific dose adjustment; however, elderly patients may be more sensitive to fluid retention and androgenic effects. Use lowest effective dose and monitor for sodium retention, hypertension, and prostatic hypertrophy.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for WINSTROL (WINSTROL).

Breastfeeding	Winstrol is contraindicated during breastfeeding. Androgens are excreted in human milk in small amounts, but there is a potential for serious adverse reactions in the nursing infant, including virilization and growth abnormalities. The M/P ratio is not determined. Alternative agents with proven safety should be used.
Teratogenic Risk	Winstrol (stanozolol) is an androgen and anabolic steroid. It is contraindicated in pregnancy. Androgens can cause virilization of the female fetus. Risk is highest during the first trimester. Exposure in the second and third trimesters may also lead to clitoral enlargement, labial fusion, and other masculinizing effects.

Warnings & precautions

■ FDA Black Box Warning

None explicitly listed, but use in sports is prohibited due to potential adverse effects.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to stanozolol","Pregnancy","Breast cancer in males","Prostate cancer","Nephrotic syndrome","Severe hepatic impairment"]

Clinical Precautions

Precautions

["Hepatotoxicity: risk of peliosis hepatis and hepatic neoplasms","Lipid profile changes: decreased HDL, increased LDL","Cardiovascular risk: hypertension, left ventricular hypertrophy","Endocrine: virilization, menstrual irregularities, gynecomastia, decreased spermatogenesis","Growth suppression in children","Glucose intolerance"]

Clinical Tips & Counseling

Drug interactions

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WINSTROL

Clinical safety rating: caution

Comprehensive clinical and safety monograph for WINSTROL (WINSTROL).

How it works

What the body does with it

Metabolism	Hepatic; primarily via reduction and conjugation, metabolized by enzymes such as 3α-hydroxysteroid dehydrogenase and glucuronosyltransferases.
Excretion	Primarily renal: 90% as metabolites (glucuronide and sulfate conjugates) and 10% as unchanged drug; minor biliary/fecal elimination (<5%).
Half-life	Terminal elimination half-life: 9-10 hours for oral administration (stanozolol); parenteral (IM) half-life extends to ~24 hours due to slow release from injection site. Clinical context: supports once-daily oral dosing or weekly IM dosing.
Protein binding	Approximately 94% bound to serum albumin and sex hormone-binding globulin (SHBG).
Volume of Distribution	Apparent Vd: ~0.3 L/kg (range 0.2-0.4 L/kg) for oral; reflects moderate distribution into extravascular tissues, with preferential binding to muscle and androgen receptors.
Bioavailability	Oral: ~3% due to extensive first-pass metabolism (stanozolol is 17α-alkylated, reducing bioavailability). Intramuscular: 100% bioavailable (parent compound released from injection site).
Onset of Action	Oral: 1-3 hours for initial effects (e.g., increased protein synthesis). Intramuscular: 2-4 hours; peak plasma concentrations at 24-48 hours post IM.
Duration of Action	Oral: 6-8 hours for single dose; with chronic dosing, effects (anabolic, androgenic) persist for several days. IM (aqueous suspension): duration of 2-3 weeks due to slow absorption; clinical effect lasts for 1-2 weeks after last dose.

Classification & Brands

Dosing & administration

Adults: 2 mg orally three times daily, or 50 mg/mL intramuscularly once monthly (3-4 week intervals) for anabolic effect. Dose range: 1-3 mg/kg/day for hereditary angioedema.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild to moderate renal impairment. For severe impairment (GFR <30 mL/min), use with caution; limited data suggest no dose adjustment but monitor fluid balance due to potential sodium and water retention.
Liver impairment	Contraindicated in severe hepatic disease. In Child-Pugh class A (mild), use with caution; no specific dose adjustment. In Child-Pugh class B or C (moderate to severe), avoid use due to risk of hepatotoxicity.
Pediatric use	Weight-based: 0.05-0.2 mg/kg/day orally for anabolic effect. For hereditary angioedema, 2-4 mg/day in children aged 6-12 years. Parenteral dose: 0.5-1 mg/kg intramuscularly once monthly. Not recommended in prepubertal children due to potential premature epiphyseal closure.
Geriatric use	No specific dose adjustment; however, elderly patients may be more sensitive to fluid retention and androgenic effects. Use lowest effective dose and monitor for sodium retention, hypertension, and prostatic hypertrophy.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for WINSTROL (WINSTROL).

Breastfeeding	Winstrol is contraindicated during breastfeeding. Androgens are excreted in human milk in small amounts, but there is a potential for serious adverse reactions in the nursing infant, including virilization and growth abnormalities. The M/P ratio is not determined. Alternative agents with proven safety should be used.
Teratogenic Risk	Winstrol (stanozolol) is an androgen and anabolic steroid. It is contraindicated in pregnancy. Androgens can cause virilization of the female fetus. Risk is highest during the first trimester. Exposure in the second and third trimesters may also lead to clitoral enlargement, labial fusion, and other masculinizing effects.

Warnings & precautions

■ FDA Black Box Warning

None explicitly listed, but use in sports is prohibited due to potential adverse effects.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to stanozolol","Pregnancy","Breast cancer in males","Prostate cancer","Nephrotic syndrome","Severe hepatic impairment"]