FLUOXYMESTERONE

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FLUOXYMESTERONE (FLUOXYMESTERONE).

How it works

Synthetic androgen receptor agonist; binds to androgen receptors, modulating gene expression and promoting protein synthesis, muscle growth, and secondary sexual characteristic development.

What the body does with it

Metabolism	Primarily hepatic metabolism via reduction and conjugation; excreted in urine.
Excretion	Renal: 90% as glucuronide and sulfate conjugates; fecal: 10%
Half-life	Terminal elimination half-life: 9.2 hours; clinical context: supports once-daily dosing for androgen replacement, with steady-state achieved in ~2 days
Protein binding	98% bound to sex hormone-binding globulin (SHBG) and albumin
Volume of Distribution	Vd: 1.5 L/kg (range 0.5-3.0 L/kg); clinical meaning: moderate to large distribution into tissues, including muscle and liver
Bioavailability	Oral: approximately 75-80%, with interindividual variability due to first-pass metabolism; not administered parenterally
Onset of Action	Oral: 1-2 hours for androgenic effects (e.g., voice deepening); maximum effect at 4-6 hours
Duration of Action	Oral: Androgenic effects persist for 24-48 hours; clinical note: duration of action sufficient for daily dosing in hypogonadism, but short half-life may require multiple daily doses for some effects

Classification & Brands

Dosing & administration

Adults: 5-20 mg orally once daily. For replacement therapy, 5-10 mg daily; for hypogonadism, 5-20 mg daily for several months.

Dosage form	TABLET
Renal impairment	No specific guidelines; use with caution in patients with severe renal impairment (CrCl <30 mL/min) due to potential fluid retention.
Liver impairment	Contraindicated in patients with severe hepatic impairment (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), consider dose reduction (e.g., 50% of usual dose) and monitor liver function.
Pediatric use	Not recommended for use in children due to risk of premature epiphyseal closure and virilization. If used for specific conditions (e.g., delayed puberty in males), dose: 2.5-5 mg orally once daily for 4-6 months.
Geriatric use	Use with caution; lower initial doses (e.g., 2.5-5 mg orally once daily) due to increased risk of prostatic hypertrophy, fluid retention, and cardiovascular events.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for FLUOXYMESTERONE (FLUOXYMESTERONE).

Breastfeeding	Fluoxymesterone is excreted into breast milk; M/P ratio not available. It may cause virilization in male infants or androgenic effects in female infants. Due to potential serious adverse effects, breastfeeding is generally contraindicated during fluoxymesterone therapy.
Teratogenic Risk	Fluoxymesterone is contraindicated in pregnancy. It is an androgen and can cause virilization of the female fetus. First trimester exposure risks clitoral enlargement, labial fusion, and other ambiguous genitalia. Second and third trimester exposure may cause clitoral enlargement and other masculinizing effects. There is also potential for growth retardation and adverse pregnancy outcomes.

Warnings & precautions

■ FDA Black Box Warning

Hepatotoxicity: Prolonged use at high doses associated with severe hepatic effects including peliosis hepatis, hepatocellular carcinoma, and hepatic necrosis. Contraindicated in patients with existing liver disease.

Side Effect Profile

Serious Effects

Absolute Contraindications

Severe hepatic dysfunction; known or suspected prostate or breast carcinoma in males; women who are or may become pregnant; hypersensitivity to fluoxymesterone or any component.

Clinical Precautions

Precautions

Monitor liver function; risk of cholestatic hepatitis. May cause fluid retention, hypercalcemia, gynecomastia, prostatic hypertrophy, and polycythemia. In females, virilization; in prepubertal males, premature epiphyseal closure. Use in athletes for performance enhancement is banned.

Clinical Tips & Counseling

Drug interactions

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FLUOXYMESTERONE

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FLUOXYMESTERONE (FLUOXYMESTERONE).

How it works

Synthetic androgen receptor agonist; binds to androgen receptors, modulating gene expression and promoting protein synthesis, muscle growth, and secondary sexual characteristic development.

What the body does with it

Metabolism	Primarily hepatic metabolism via reduction and conjugation; excreted in urine.
Excretion	Renal: 90% as glucuronide and sulfate conjugates; fecal: 10%
Half-life	Terminal elimination half-life: 9.2 hours; clinical context: supports once-daily dosing for androgen replacement, with steady-state achieved in ~2 days
Protein binding	98% bound to sex hormone-binding globulin (SHBG) and albumin
Volume of Distribution	Vd: 1.5 L/kg (range 0.5-3.0 L/kg); clinical meaning: moderate to large distribution into tissues, including muscle and liver
Bioavailability	Oral: approximately 75-80%, with interindividual variability due to first-pass metabolism; not administered parenterally
Onset of Action	Oral: 1-2 hours for androgenic effects (e.g., voice deepening); maximum effect at 4-6 hours
Duration of Action	Oral: Androgenic effects persist for 24-48 hours; clinical note: duration of action sufficient for daily dosing in hypogonadism, but short half-life may require multiple daily doses for some effects

Classification & Brands

Dosing & administration

Adults: 5-20 mg orally once daily. For replacement therapy, 5-10 mg daily; for hypogonadism, 5-20 mg daily for several months.

Dosage form	TABLET
Renal impairment	No specific guidelines; use with caution in patients with severe renal impairment (CrCl <30 mL/min) due to potential fluid retention.
Liver impairment	Contraindicated in patients with severe hepatic impairment (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), consider dose reduction (e.g., 50% of usual dose) and monitor liver function.
Pediatric use	Not recommended for use in children due to risk of premature epiphyseal closure and virilization. If used for specific conditions (e.g., delayed puberty in males), dose: 2.5-5 mg orally once daily for 4-6 months.
Geriatric use	Use with caution; lower initial doses (e.g., 2.5-5 mg orally once daily) due to increased risk of prostatic hypertrophy, fluid retention, and cardiovascular events.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for FLUOXYMESTERONE (FLUOXYMESTERONE).

Breastfeeding	Fluoxymesterone is excreted into breast milk; M/P ratio not available. It may cause virilization in male infants or androgenic effects in female infants. Due to potential serious adverse effects, breastfeeding is generally contraindicated during fluoxymesterone therapy.
Teratogenic Risk	Fluoxymesterone is contraindicated in pregnancy. It is an androgen and can cause virilization of the female fetus. First trimester exposure risks clitoral enlargement, labial fusion, and other ambiguous genitalia. Second and third trimester exposure may cause clitoral enlargement and other masculinizing effects. There is also potential for growth retardation and adverse pregnancy outcomes.

Warnings & precautions

■ FDA Black Box Warning

Side Effect Profile

Serious Effects

Absolute Contraindications

Severe hepatic dysfunction; known or suspected prostate or breast carcinoma in males; women who are or may become pregnant; hypersensitivity to fluoxymesterone or any component.