JATENZO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for JATENZO (JATENZO).
JATENZO (testosterone undecanoate) is a testosterone replacement therapy. Testosterone acts as an androgen receptor agonist, binding to and activating androgen receptors, which leads to modulation of gene expression and physiological effects such as development of male sexual characteristics, maintenance of muscle mass, bone density, and erythropoiesis.
| Metabolism | Primarily metabolized via the liver, involving reduction, oxidation, and conjugation. The major metabolites are androsterone and etiocholanolone, which are excreted as glucuronide and sulfate conjugates. CYP3A4 may play a minor role in oxidation. |
| Excretion | Primarily renal (90% as conjugated metabolites, ~10% unchanged); minor fecal (approximately 5%) |
| Half-life | Approximately 10-15 hours (terminal elimination half-life in hypogonadal males; supports once-daily dosing) |
| Protein binding | 98% bound to sex hormone-binding globulin (SHBG) and albumin |
| Volume of Distribution | Approximately 1-1.5 L/kg, reflecting extensive distribution into tissues |
| Bioavailability | Approximately 12-14% (oral, with food; significant interindividual variability) |
| Onset of Action | Oral: serum testosterone concentrations rise within 6 hours, reaching peak at 8-12 hours |
| Duration of Action | Maintains serum testosterone within eugonadal range over 24-hour dosing interval with once-daily oral administration |
| Molecular Weight | 288.42 |
Oral, starting dose 237 mg twice daily with food. Titrate based on testosterone levels, maximum 396 mg twice daily.
| Dosage form | CAPSULE |
| Renal impairment | No dose adjustment required for mild to moderate impairment (eGFR ≥30 mL/min/1.73m²). Not recommended in severe impairment (eGFR <30 mL/min/1.73m²) due to lack of data. |
| Liver impairment | Child-Pugh Class A or B: No dose adjustment. Child-Pugh Class C: Not studied, avoid use. |
| Pediatric use | Not approved for use in pediatric patients <18 years. |
| Geriatric use | Limited data in patients ≥65 years. Use with caution, monitor for adverse effects related to polycythemia and prostate disorders. |
| 1st trimester | Contraindicated due to risk of masculinization of female fetus, including clitoromegaly, labial fusion, and other virilizing effects. Testosterone exposure during early pregnancy can disrupt normal sexual differentiation. |
| 2nd trimester | Contraindicated. Continued risk of virilization of female fetus. Androgenic effects may also affect maternal health, including potential for hepatic dysfunction. |
| 3rd trimester | Contraindicated. Late exposure may still cause clitoromegaly and other virilizing changes. Additionally, maternal adverse effects such as cholestatic jaundice may occur. |
Clinical note
Comprehensive clinical and safety monograph for JATENZO (JATENZO).
| Placental transfer | Testosterone readily crosses the placenta. Studies have demonstrated that exogenous testosterone administration leads to significant fetal exposure, resulting in virilization of female offspring and potential disruption of normal genital development. |
| Breastfeeding |
■ FDA Black Box Warning
WARNING: SECONDARY EXPOSURE TO TESTOSTERONE. Cases of secondary exposure to testosterone resulting in virilization of children have been reported following use of topical testosterone products. JATENZO is an oral capsule, but similar risks may apply if capsules are not handled properly. Additionally, androgens are not indicated for use in women.
| Serious Effects |
PregnancyBreastfeedingMen with breast cancerMen with known or suspected prostate cancerKnown hypersensitivity to testosterone or any component of JATENZO
| Precautions | Secondary exposure to testosterone (risk to children), Hepatotoxicity (rare cases of cholestatic hepatitis, jaundice reported with oral methyltestosterone; monitor liver function), Polycythemia (increased hematocrit, monitor periodically), Worsening of benign prostatic hyperplasia (BPH) or prostate cancer risk, Edema (use with caution in patients with cardiac, renal, or hepatic disease), Hypercalcemia in immobilized patients or those with bone metastases, Sleep apnea, Lipid profile changes (decreased HDL), Macrovirilization in women (if exposed), Potential for anabolic steroid abuse |
| Food/Dietary |
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| Contraindicated during breastfeeding. Testosterone and its metabolites are excreted in breast milk and may cause virilization in the infant, including accelerated growth and behavioral changes. Alternative therapies should be considered. |
| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | JATENZO (testosterone undecanoate) is contraindicated in pregnancy. Testosterone exposure during the first trimester may cause virilization of female fetal genitalia, including clitoromegaly and labial fusion. No adequate studies in pregnant women; animal studies show adverse effects on fetal development. Risk cannot be ruled out in all trimesters. |
| Fetal Monitoring | Monitor maternal blood pressure, hematocrit, lipid profile, and liver function tests periodically. If inadvertent use during pregnancy occurs, monitor fetal development via ultrasound for signs of virilization. |
| Fertility Effects | Exogenous testosterone may suppress endogenous testosterone production via negative feedback on the hypothalamic-pituitary-gonadal axis, leading to reduced spermatogenesis and impaired fertility in males. Reversible upon discontinuation. In females, appropriate use is not indicated for fertility; effects on female fertility are not studied. |
| Must be taken with a meal containing at least 20 g of fat (e.g., 2 tablespoons of peanut butter, 1 oz of almonds, or a standard fatty meal) to ensure adequate absorption. Grapefruit juice may increase testosterone levels; avoid concurrent consumption. |
| Clinical Pearls | JATENZO (oral testosterone undecanoate) is a prodrug absorbed via the lymphatic system, requiring administration with a fatty meal (at least 20 g fat) to ensure adequate absorption. Avoid substitution with other testosterone products due to differing pharmacokinetics. Monitor serum testosterone levels 3–5 hours post-dose after at least 14 days of therapy. Contraindicated in men with breast or prostate cancer, and in patients with known hypersensitivity. Use with caution in patients with conditions exacerbated by androgens (e.g., sleep apnea, heart failure, hypertension). |
| Patient Advice | Take JATENZO exactly as prescribed with a meal containing at least 20 grams of fat to ensure proper absorption. · Do not substitute JATENZO with other testosterone products as doses are not equivalent. · Regular blood tests are required to monitor testosterone levels and other health parameters. · Report any signs of blood clots, such as pain, swelling, or redness in legs, or sudden chest pain or shortness of breath. · Inform your healthcare provider about all medications and supplements you are taking. · Store JATENZO capsules at room temperature, away from moisture and heat, and keep out of reach of children. |