HALOTESTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HALOTESTIN (HALOTESTIN).
Fluoxymesterone is a synthetic androgen that binds to androgen receptors, activating gene transcription and promoting protein synthesis, leading to anabolic and androgenic effects.
| Metabolism | Hepatic via CYP3A4 |
| Excretion | Renal: 90% as glucuronide and sulfate conjugates; fecal: 10%. |
| Half-life | Terminal elimination half-life: 9.6 hours. Clinical context: Steady-state achieved after ~48 hours. |
| Protein binding | 98% bound to sex hormone-binding globulin (SHBG) and albumin. |
| Volume of Distribution | Vd: 0.5-0.8 L/kg, indicating distribution into total body water and some tissue binding. |
| Bioavailability | Oral: 10-20% due to extensive first-pass metabolism; IM: 100%. |
| Onset of Action | Oral: 1-2 hours for androgenic effects; IM: 24-48 hours. |
| Duration of Action | Oral: 6-8 hours for replacement therapy; IM: 2-4 weeks for depot effects. |
| Molecular Weight | 336.46 |
10-20 mg orally three to four times daily for replacement therapy; 2-10 mg orally daily for delayed puberty in males.
| Dosage form | TABLET |
| Renal impairment | GFR <30 mL/min: use with caution; reduce dose to 5-10 mg twice daily. GFR <10 mL/min: avoid use. |
| Liver impairment | Child-Pugh class A: no adjustment. Child-Pugh class B: reduce dose by 50%. Child-Pugh class C: contraindicated. |
| Pediatric use | For delayed puberty: 2.5-5 mg orally daily for up to 6 months; titrate based on response. Not recommended for prepubertal children. |
| Geriatric use | Start with lowest effective dose (2.5 mg orally daily) to minimize risk of prostatic hypertrophy and fluid retention. |
| 1st trimester | Contraindicated: Androgenic effects may cause fetal harm, including masculinization of female fetuses. |
| 2nd trimester | Contraindicated: Risk of virilization of female fetus and potential skeletal abnormalities. |
| 3rd trimester | Contraindicated: Potential for fetal harm; may cause virilization and premature skeletal maturation. |
Clinical note
Comprehensive clinical and safety monograph for HALOTESTIN (HALOTESTIN).
| Placental transfer | Androgens such as fluoxymesterone are known to cross the placenta. Animal studies and case reports suggest significant transfer, leading to fetal effects. |
| Breastfeeding | Excretion into breast milk is unknown; potential for serious adverse effects in nursing infants, including virilization and bone growth acceleration. Use is not recommended during breastfeeding. |
■ FDA Black Box Warning
Prolonged use of androgens has been associated with development of hepatocellular carcinoma and peliosis hepatis.
| Serious Effects |
Hypersensitivity to fluoxymesterone or any componentCarcinoma of the male breastCarcinoma of the prostatePregnancyNephrosis or nephrotic phase of nephritisHypercalcemia
| Precautions | Monitor for signs of virilization in women, fluid retention, hypercalcemia, and hepatic dysfunction. May cause priapism in men. Use with caution in patients with cardiac, renal, or hepatic disease. |
| Food/Dietary | Avoid excessive grapefruit juice as it may inhibit CYP3A4 metabolism, increasing halotestin levels. Avoid high-sodium foods to reduce fluid retention and hypertension risk. No other significant food interactions known. |
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| Lactation Rating |
| Avoid |
| Teratogenic Risk | Pregnancy Category X. Contraindicated in all trimesters due to virilization of female fetus (clitoral enlargement, labial fusion) and potential for skeletal abnormalities. Androgenic effects may occur at any gestational age. |
| Fetal Monitoring | Monitor maternal hepatic function, lipid profile, and signs of virilization (e.g., hirsutism, voice deepening). If inadvertent exposure occurs, fetal ultrasound to assess genital anatomy and growth. |
| Fertility Effects | May suppress gonadotropin secretion and cause oligospermia or azoospermia in males. In females, may disrupt menstrual cycle and reduce fertility. Effects are reversible upon discontinuation. |
| Clinical Pearls | Monitor liver function tests regularly due to risk of hepatotoxicity. Use with caution in patients with cardiovascular disease due to fluid retention and potential for exacerbation of hypertension. Check lipid profile periodically as androgens can lower HDL cholesterol. Avoid in prostate cancer or male breast cancer. May cause priapism; instruct patient to seek immediate medical attention if erection lasts >4 hours. Can suppress endogenous testosterone; monitor for hypogonadism after discontinuation. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency without doctor approval. · Report any signs of liver problems: yellowing of skin/eyes, dark urine, abdominal pain, or persistent nausea. · Seek immediate medical help if you experience painful erections lasting more than 4 hours. · Tell your doctor if you have heart disease, high blood pressure, or diabetes before starting treatment. · Do not take if pregnant or breastfeeding; can cause harm to fetus or infant. · Keep all appointments for blood tests to monitor liver function, cholesterol, and red blood cell count. |