ORETON METHYL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ORETON METHYL (ORETON METHYL).
Methyltestosterone is a synthetic androgen that binds to androgen receptors, activating transcription of androgen-responsive genes, leading to increased protein synthesis, muscle growth, and secondary sexual characteristic development.
| Metabolism | Hepatic via CYP3A4; undergoes extensive first-pass metabolism, resulting in low oral bioavailability. |
| Excretion | Primarily renal as conjugated metabolites; ~90% urinary, ~6% fecal within 4 days. |
| Half-life | Terminal half-life approximately 2.7–3.8 hours; brief due to rapid hepatic metabolism. |
| Protein binding | ~97–99% bound primarily to sex hormone-binding globulin (SHBG) and albumin. |
| Volume of Distribution | 0.4–0.6 L/kg; moderate distribution, mainly to muscle and prostate. |
| Bioavailability | Oral: low ~6% due to first-pass metabolism. IM: 100%. Buccal: ~20–25%. |
| Onset of Action | IM: 1–2 hours for androgenic effects. Oral: 2–4 hours; buccal: rapid absorption within minutes. |
| Duration of Action | IM: Up to 2–3 weeks (depot formulation). Oral: 4–6 hours. Buccal: 2–4 hours. |
10-50 mg orally or buccally 1-3 times daily; or 25-100 mg IM every 2-4 weeks.
| Dosage form | TABLET |
| Renal impairment | Not specifically required; caution in severe renal impairment due to potential fluid retention. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh C). In moderate impairment (Child-Pugh B), reduce dose by 50% or use with caution. |
| Pediatric use | Not recommended for use in children; safety and efficacy not established. |
| Geriatric use | Use with caution; monitor for prostate enlargement, fluid retention, and cardiovascular effects. Start at lower end of dosing range. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ORETON METHYL (ORETON METHYL).
| Breastfeeding | Methyltestosterone is excreted into breast milk. The M/P ratio is not established. Potential for adverse effects in the nursing infant, including virilization, and suppression of lactation. Breastfeeding is not recommended. |
| Teratogenic Risk | Androgenic progestins like methyltestosterone (ORETON METHYL) are associated with virilization of female fetuses, including clitoromegaly and labial fusion, particularly during the first trimester. Use in pregnancy is contraindicated. |
| Fetal Monitoring |
■ FDA Black Box Warning
Prolonged use of high doses of methyltestosterone has been associated with serious hepatic adverse effects, including peliosis hepatis, hepatic neoplasms, and hepatocellular carcinoma.
| Serious Effects |
Known or suspected prostate cancer; male breast cancer; hypersensitivity to methyltestosterone; pregnancy; breastfeeding; severe hepatic impairment.
| Precautions | Monitor liver function; risk of hepatic toxicity including cholestatic hepatitis and jaundice; may cause fluid retention, especially in patients with cardiac, renal, or hepatic disease; may cause hypercalcemia in immobile patients or those with metastatic breast cancer; may suppress spermatogenesis; may cause gynecomastia; may accelerate bone maturation in children; may cause priapism; may affect serum lipids; may cause polycythemia; use with caution in patients with diabetes (may alter insulin sensitivity). |
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| Monitor maternal liver function tests due to hepatotoxicity risk. Assess fetal growth and development if inadvertent exposure occurs. Consider ultrasound for fetal genital anomalies if exposure in first trimester. |
| Fertility Effects | Methyltestosterone may suppress ovulation and endometrial development, impairing fertility. Use as a component of hormone therapy in transgender men may cause amenorrhea and anovulation. |