WINSTROL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for WINSTROL (WINSTROL).
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.
| 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. |
| Molecular Weight | 328.45 Da |
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. |
| 1st trimester | Contraindicated. Androgens can cause virilization of female fetus, clitoral enlargement, labial fusion, and ambiguous genitalia. Risk of masculinization of female fetus is highest during first trimester. |
| 2nd trimester | Contraindicated. Continued risk of virilization of female fetus; may cause skeletal abnormalities and growth retardation. |
| 3rd trimester | Contraindicated. Risk of virilization persists; may cause premature closure of epiphyses and potential for long-term growth effects. |
Clinical note
Comprehensive clinical and safety monograph for WINSTROL (WINSTROL).
| Placental transfer | Androgens readily cross the placenta; evidence from case reports of virilization in female infants confirms significant transfer. |
| Breastfeeding | Excreted in breast milk; may cause virilization in nursing infants. Discontinue breastfeeding or avoid use due to risk of androgen exposure. |
■ FDA Black Box Warning
None explicitly listed, but use in sports is prohibited due to potential adverse effects.
| Serious Effects |
Pregnancy (all trimesters)BreastfeedingBreast cancer (in males with hypercalcemia)Prostate cancer (androgen-dependent)Nephrotic syndrome (especially in pediatric patients)Hypersensitivity to stanozolol or any componentSevere hepatic impairmentCardiac or renal insufficiency (due to fluid retention risk)
| 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 |
| Food/Dietary | Avoid grapefruit juice as it may increase drug levels. Limit alcohol to reduce hepatotoxicity. High-fat meals may increase absorption; take consistently with meals to maintain stable levels. |
Loading safety data…
| Lactation Rating | L5 (Contraindicated) |
| 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. |
| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes, and liver function tests due to risk of hypertension, edema, and hepatotoxicity. Monitor fetal growth and development via ultrasound if inadvertent exposure occurs. Observe for signs of virilization in the infant. |
| Fertility Effects | Winstrol may impair fertility in both males and females. In females, it can cause menstrual irregularities, anovulation, and suppression of ovulation due to negative feedback on gonadotropins. In males, it may reduce spermatogenesis and cause oligospermia or azoospermia. Effects may be reversible upon discontinuation. |
| Clinical Pearls | Monitor liver function tests regularly due to hepatotoxicity risk; avoid in patients with pre-existing hepatic impairment. Watch for virilization in women and gynecomastia in men. Consider QT prolongation risk. Discontinue if hypercalcemia develops. Not recommended for use in children due to premature epiphyseal closure. |
| Patient Advice | Take with food to minimize gastrointestinal upset. · Report any signs of jaundice (yellowing of skin/eyes), dark urine, or pale stools immediately. · Women should report any voice deepening, excessive hair growth, or menstrual irregularities. · Men should report any breast tenderness or enlargement. · Avoid alcohol consumption due to increased liver stress. · Do not use during pregnancy or if planning to become pregnant. · May cause fluid retention; report unusual swelling or weight gain. · Adhere to prescribed dose; do not adjust without consulting provider. |