VIRILON
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VIRILON (VIRILON).
Testosterone replacement therapy; binds to androgen receptors, leading to activation of androgen-responsive genes and promotion of male secondary sexual characteristics.
| Metabolism | Primarily hepatic via CYP3A4 and other CYP450 enzymes; metabolites are excreted in urine. |
| Excretion | Approximately 90% of administered methyltestosterone is excreted as glucuronide and sulfate conjugates in urine; less than 5% appears in feces as unchanged drug and metabolites. |
| Half-life | Terminal elimination half-life is approximately 3–4 hours for methyltestosterone; however, the pharmacologic effect persists longer due to active metabolites, supporting once-daily dosing. |
| Protein binding | Approximately 95% bound to plasma proteins, primarily sex hormone-binding globulin (SHBG) and albumin. |
| Volume of Distribution | Apparent volume of distribution is approximately 0.5–1.0 L/kg, indicating distribution into total body water with some tissue binding. |
| Bioavailability | Oral bioavailability is approximately 40–60% due to extensive first-pass metabolism in the liver. Sublingual administration may achieve higher systemic exposure. |
| Onset of Action | Oral: Peak plasma concentrations occur within 1–2 hours; clinical effects (e.g., virilization) may be observed after several days of continuous therapy. |
| Duration of Action | The clinical duration of action is approximately 24 hours due to once-daily dosing, but effects on anabolic processes may persist for several days after discontinuation. |
| Molecular Weight | 288.43 |
200 mg intramuscularly every 2 weeks for androgen replacement therapy in adult males.
| Dosage form | CAPSULE |
| Renal impairment | No dose adjustment required for renal impairment. Use with caution in patients with nephrotic syndrome due to potential fluid retention. |
| Liver impairment | Contraindicated in patients with severe hepatic impairment (Child-Pugh Class C). For moderate impairment (Child-Pugh Class B), reduce dose to 100 mg every 2 weeks and monitor liver function. |
| Pediatric use | Not recommended for use in pediatric patients. Safety and efficacy have not been established; may cause premature epiphyseal closure and virilization. |
| Geriatric use | Use with caution in elderly patients due to increased risk of prostatic hypertrophy and prostatic carcinoma. Monitor prostate-specific antigen (PSA) regularly. Consider lower starting dose of 100 mg every 2 weeks. |
| 1st trimester | Avoid due to teratogenicity risk from androgenic effects; may cause pseudohermaphroditism in female fetuses. |
| 2nd trimester | Avoid; masculinization of female fetus and advanced bone age in both sexes reported. |
| 3rd trimester | Avoid; risk of vitilization of female fetus and premature closure of epiphyses. |
Clinical note
Comprehensive clinical and safety monograph for VIRILON (VIRILON).
| Placental transfer | Extensive placental transfer documented; crosses to achieve fetal concentrations similar to maternal levels. |
| Breastfeeding | Excreted in breast milk; use caution due to potential virilization of female infants and acceleration of growth in male infants. Consider alternative agents if breastfeeding. |
| Lactation Rating |
■ FDA Black Box Warning
WARNING: Use in men with breast cancer or known/suspected prostate cancer is contraindicated. Risk of accelerated growth of prostate cancer and exacerbation of breast cancer.
| Serious Effects |
PregnancyUndiagnosed genital bleedingProstate carcinomaBreast cancer in malesSevere hepatic dysfunctionHypercalcemia due to malignancy
| Precautions | Monitor for prostate cancer risk (PSA, digital rectal exam), Risk of polycythemia (increased hematocrit), Fluid retention and edema, Gynecomastia, Sleep apnea, Hepatotoxicity (with oral formulations), Decreased spermatogenesis, Virilization in women, Increased risk of cardiovascular events |
| Food/Dietary | Take with food to reduce GI upset. Avoid grapefruit juice as it may increase methyltestosterone levels. Alcohol consumption may exacerbate hepatotoxicity. |
Loading safety data…
| L3 (Moderately Safe) - limited data suggest risk, but often acceptable with monitoring. |
| Teratogenic Risk | Testosterone esters (e.g., testosterone cypionate, testosterone enanthate) are contraindicated in pregnancy. Androgens can cause virilization of the female fetus, including clitoromegaly, labial fusion, and urogenital sinus abnormalities, especially during the first trimester when genital differentiation occurs. Risk is dose-dependent and increases with higher maternal androgen levels. No adequate human studies; animal studies show teratogenic effects at high doses. |
| Fetal Monitoring | Monitor maternal blood pressure, liver function tests, lipid profile, and signs of virilization (e.g., hirsutism, acne, voice deepening). Serial fetal ultrasound for assessment of genital development if accidental exposure occurs during pregnancy. Monitor for maternal hepatotoxicity and polycythemia. |
| Fertility Effects | Exogenous androgens can suppress gonadotropin secretion, leading to reversible oligospermia or azoospermia in males and ovulatory dysfunction in females. This may impair fertility during use. Effects are generally reversible upon discontinuation. In females, androgens may disrupt menstrual cycles and reduce fertility. Use in men with hypogonadism may restore fertility if hypogonadism is the cause of infertility. |
| Clinical Pearls | VIRILON (methyltestosterone) is an androgen used for testosterone replacement therapy. Monitor liver function tests due to risk of hepatotoxicity. Avoid in patients with prostate or breast cancer. May cause priapism, gynecomastia, and edema. Use with caution in elderly due to increased risk of prostatic hyperplasia. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency. · Report symptoms of priapism (prolonged erection), jaundice, or edema immediately. · Regular blood tests (liver function, PSA, lipid profile) are required. · Avoid alcohol as it may increase risk of liver damage. · Women of childbearing age should use effective contraception due to potential virilization of fetus. · Do not use if you have a history of prostate or breast cancer. |