Introduction
Jatenzo (testosterone undecanoate) is an oral androgen replacement therapy approved by the FDA in 2019 for testosterone replacement therapy in adult males for conditions associated with a deficiency or absence of endogenous testosterone. It represents a significant advancement in testosterone delivery systems as the first FDA-approved oral testosterone capsule that doesn't require dose titration with meals.
Mechanism of Action
Testosterone undecanoate is hydrolyzed to testosterone in the body. Testosterone is the primary endogenous androgen that stimulates receptors in target tissues to promote and maintain male sexual characteristics. It exerts its effects through binding to androgen receptors in various tissues, leading to genomic and non-genomic effects that result in:
- Development and maintenance of male sexual characteristics
- Promotion of nitrogen retention and protein anabolism
- Stimulation of erythropoiesis
- Regulation of bone mineral density
Indications
Jatenzo is indicated for testosterone replacement therapy in adult males for conditions associated with a deficiency or absence of endogenous testosterone:
- Primary hypogonadism (congenital or acquired)
- Hypogonadotropic hypogonadism (congenital or acquired)
Dosage and Administration
Initial dosing: 237 mg twice daily with food Dose adjustment: Based on serum testosterone concentrations measured 6-8 hours after dosing, with a target range of 400-700 ng/dL Dose titration: May increase to 316 mg twice daily or decrease to 158 mg twice daily based on testosterone levels Administration: Must be taken with food to enhance absorption Special populations:- Renal impairment: No dosage adjustment necessary
- Hepatic impairment: Not recommended in patients with hepatic impairment
- Geriatric patients: Use with caution
Pharmacokinetics
Absorption: Testosterone undecanoate is absorbed via the lymphatic system, bypassing first-pass metabolism. Bioavailability is approximately 7% when administered with food. Distribution: Testosterone is approximately 98% bound to sex hormone-binding globulin (SHBG) and albumin. Metabolism: Primarily metabolized in the liver via CYP3A4 to various metabolites including dihydrotestosterone (DHT) and estradiol. Elimination: Testosterone and its metabolites are excreted primarily in urine (90%) and feces (6%). Half-life is approximately 1.3 hours for testosterone undecanoate.Contraindications
- Men with breast cancer
- Men with known or suspected prostate cancer
- Pregnancy (may cause fetal harm)
- Hypersensitivity to testosterone undecanoate or any component of Jatenzo
- Patients with serious cardiac, hepatic, or renal disease
Warnings and Precautions
Blood pressure increases: Jatenzo can increase blood pressure, increasing risk of major adverse cardiovascular events (MACE) Cardiovascular risk: May increase risk of myocardial infarction, stroke, and cardiovascular death Erythrocytosis: Can cause polycythemia, which may require dose reduction or discontinuation Benign prostatic hyperplasia (BPH) worsening: May worsen BPH symptoms Potential for secondary exposure: Can transfer to others through contact Hepatic effects: Prolonged use may cause hepatic dysfunction Sleep apnea: May exacerbate sleep apnea Edema: May cause fluid retention, particularly in patients with cardiac, renal, or hepatic diseaseDrug Interactions
CYP3A4 inducers: (e.g., rifampin, carbamazepine, phenytoin) - May decrease testosterone concentrations CYP3A4 inhibitors: (e.g., ketoconazole, ritonavir) - May increase testosterone concentrations Corticosteroids: May enhance fluid retention Insulin: May decrease blood glucose levels Oral anticoagulants: May alter anticoagulant requirementsAdverse Effects
Most common adverse reactions (≥2%):- Increased hematocrit (51%)
- Headache (13%)
- Increased HDL (10%)
- Hypertension (8%)
- Decreased HDL (5%)
- Nausea (4%)
- Major adverse cardiovascular events
- Venous thromboembolism
- Erythrocytosis requiring phlebotomy
- Hepatotoxicity
- Psychiatric effects including depression, aggression, and mood changes
Monitoring Parameters
Before initiation:- Testosterone levels (confirm hypogonadism)
- Prostate-specific antigen (PSA) and digital rectal exam
- Hematocrit/hemoglobin
- Lipid profile
- Cardiovascular risk assessment
- Serum testosterone levels (3 months after initiation, then periodically)
- Hematocrit (at 3-6 months, then annually)
- PSA (at 3-6 months, then in accordance with guidelines)
- Blood pressure (regularly)
- Lipid profile (annually)
- Liver function tests (periodically)
Patient Education
- Take exactly as prescribed with food
- Do not crush or chew capsules
- Report any of the following immediately:
- Chest pain, shortness of breath, or symptoms of heart attack - Symptoms of stroke (slurred speech, weakness) - Symptoms of blood clots (painful swelling, redness) - Difficulty breathing during sleep (sleep apnea) - Persistent erectile dysfunction
- Women and children should avoid contact with unwashed or unclothed application sites
- Regular follow-up appointments are essential for monitoring
- Inform all healthcare providers about Jatenzo use
References
1. FDA Prescribing Information: Jatenzo (testosterone undecanoate) capsules. March 2019. 2. Morgentaler A, et al. J Urol. 2020;203(1):157-164. 3. Bhasin S, et al. J Clin Endocrinol Metab. 2018;103(5):1715-1744. 4. Cunningham GR, et al. J Clin Endocrinol Metab. 2021;106(3):e1306-e1315. 5. ClinicalTrials.gov: Study of Oral Testosterone Undecanoate (Jatenzo) in Hypogonadal Men (NCT02722278). 6. Kaminetsky J, et al. J Urol. 2019;202(5):1029-1038.
This information is intended for educational purposes only and should not replace professional medical advice. Always consult with a qualified healthcare provider for personal medical guidance.