TESTOPEL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TESTOPEL (TESTOPEL).
Testosterone is an androgen receptor agonist; it binds to and activates androgen receptors, leading to changes in gene expression that promote male sexual development, maintenance of secondary sexual characteristics, and anabolic effects.
| Metabolism | Testosterone is primarily metabolized in the liver via reduction (by 5α-reductase to dihydrotestosterone and by 5β-reductase), oxidation, and conjugation (glucuronidation and sulfation). Major enzymes include 5α-reductase, CYP3A4, and UGT2B17. |
| Excretion | Renal: ~90% as glucuronide and sulfate conjugates, ~10% unchanged; fecal: ~6% via biliary elimination. |
| Half-life | Terminal half-life: 8-10 days; due to prolonged release from subcutaneous depot, effective half-life extends to 2-3 weeks. |
| Protein binding | ~98%; bound primarily to sex hormone-binding globulin (SHBG) and albumin. |
| Volume of Distribution | ~6 L/kg; reflects extensive distribution into tissues, particularly muscle, skin, and adipose. |
| Bioavailability | Subcutaneous implant: 100% (by design, as it is a depot formulation with complete absorption into systemic circulation over time). |
| Onset of Action | Subcutaneous implant: 2-4 weeks for testosterone levels to reach therapeutic range; clinical effects (libido, energy) may require 4-8 weeks. |
| Duration of Action | Depot effect: 3-6 months per 75 mg implant; duration dependent on dose and implant number, with serum levels declining gradually. |
Subcutaneous implantation: 150-450 mg every 3-6 months. Individualize based on serum testosterone levels and clinical response.
| Dosage form | PELLET |
| Renal impairment | No specific dosage adjustment required for renal impairment. Monitor serum testosterone levels and clinical response. |
| Liver impairment | Contraindicated in patients with severe hepatic impairment (Child-Pugh class C). Use with caution in mild to moderate impairment with dose titration based on serum testosterone levels and hepatic function monitoring. |
| Pediatric use | Not recommended for use in pediatric patients; safety and efficacy not established. |
| Geriatric use | Initiate at lower end of dosing range (150 mg). Monitor for signs of prostatic hyperplasia, prostate cancer, and cardiovascular events. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TESTOPEL (TESTOPEL).
| Breastfeeding | Testosterone is excreted into breast milk; M/P ratio not established. Potential for virilization in nursing infants. Breastfeeding is contraindicated during TESTOPEL therapy. |
| Teratogenic Risk | Androgens are contraindicated in pregnancy. Testosterone (TESTOPEL) is pregnancy category X. First trimester: masculinization of female fetus with clitoromegaly, labial fusion; second/third trimesters: continued virilization, potential intellectual disability. No safe trimester. |
| Fetal Monitoring |
■ FDA Black Box Warning
WARNING: SECONDARY EXPOSURE TO TESTOSTERONE. Testosterone pellets can be transferred to others through skin contact, leading to unintended androgenization. Children and women of childbearing potential are particularly at risk. Patients must wash hands thoroughly after handling pellets.
| Serious Effects |
["Known hypersensitivity to testosterone or any component of the formulation","Men with prostate cancer or breast cancer","Women who are pregnant or breastfeeding (may cause fetal harm)","Patients with known or suspected carcinoma of the breast (in males)"]
| Precautions | ["Risk of secondary exposure to testosterone through skin contact","Polycythemia (increase in hemoglobin/hematocrit) requiring monitoring","Potential for sleep apnea in patients with risk factors","Edema with or without congestive heart failure in patients with pre-existing cardiac, renal, or hepatic disease","Gynecomastia","Accelerated growth of prostatic cancer and benign prostatic hyperplasia","Increased risk of prostatic hypertrophy and prostate cancer","Monitor serum calcium levels in patients with metastatic prostate cancer due to risk of hypercalcemia","Hepatotoxicity with oral forms (not applicable to pellets)","Lipid profile changes (decrease in HDL cholesterol)","Masculinization in female patients if exposed","Use with caution in patients with diabetes mellitus (may affect glycemic control)"] |
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| Monitor maternal: liver function, lipid profile, hemoglobin/hematocrit (polycythemia), blood glucose, blood pressure; fetal: ultrasound for gestational age and growth if inadvertent exposure. |
| Fertility Effects | Exogenous testosterone suppresses spermatogenesis via negative feedback on GnRH/LH/FSH, reducing sperm count and motility; reversible after discontinuation. In females, may cause anovulation and menstrual irregularities. |