TESTRED
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TESTRED (TESTRED).
Testosterone is an androgen receptor agonist, promoting development of male secondary sexual characteristics and anabolic effects.
| Metabolism | Hepatic via CYP3A4 and other CYP enzymes; metabolites include androsterone and etiocholanolone. |
| Excretion | Approximately 90% of administered testosterone is excreted in urine as glucuronide and sulfate conjugates of testosterone and its metabolites (androsterone, etiocholanolone). About 6% is excreted in feces via bile. Unchanged testosterone excretion is negligible (<1%). |
| Half-life | Terminal elimination half-life for testosterone is 2-4 hours; testosterone enanthate has a half-life of 4-5 days due to slow release from the oily depot. Clinical context: shorter half-life requires more frequent dosing for stable serum levels. |
| Protein binding | Approximately 98-99% bound to sex hormone-binding globulin (SHBG, ~40%) and albumin (~60%) in adult males. Free testosterone fraction is ~1-2%. |
| Volume of Distribution | Volume of distribution for testosterone is approximately 0.5-1.0 L/kg, indicating distribution into total body water and tissues (e.g., muscle, prostate). Clinical meaning: wide distribution, tissue binding important for effects. |
| Bioavailability | Oral testosterone: low and variable (<10%) due to extensive first-pass metabolism; methyltestosterone: ~40-60% (resistant to hepatic metabolism). Intramuscular (enanthate): 100% (systemic). Transdermal: ~10-14% (patch), 6-12% (gel). Buccal: ~80-90%. |
| Onset of Action | Intramuscular testosterone enanthate: onset of effects (e.g., increase in serum testosterone) within 1-3 days; oral methyltestosterone: 1-2 hours; transdermal: 6-8 hours. Subcutaneous pellet: weeks. |
| Duration of Action | Intramuscular testosterone enanthate: duration of action 2-4 weeks; oral methyltestosterone: 4-6 hours; transdermal patch: 24 hours (daily application); buccal tablet: 12 hours. Clinical note: duration varies with ester, dose, and individual metabolism. |
Testosterone enanthate 200 mg intramuscularly every 2 weeks.
| Dosage form | CAPSULE |
| Renal impairment | No specific dose adjustment recommended for renal impairment; use with caution in severe renal impairment due to potential fluid retention. |
| Liver impairment | Contraindicated in patients with Child-Pugh class B or C cirrhosis. For Child-Pugh class A, use with caution and monitor liver function; no specific dose adjustment provided. |
| Pediatric use | Not recommended for use in children; safety and efficacy not established. |
| Geriatric use | Use with caution in elderly patients due to increased risk of prostatic hypertrophy and cardiovascular events; monitor prostate-specific antigen and hematocrit regularly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TESTRED (TESTRED).
| Breastfeeding | Testosterone is excreted into breast milk. M/P ratio not established. Potential adverse effects include virilization in female infants and growth acceleration. Use during breastfeeding is contraindicated. |
| Teratogenic Risk | Pregnancy Category X. Testosterone can cause virilization of female fetus, including clitoromegaly, labial fusion, and urogenital sinus abnormalities. Risk is highest during first trimester when organogenesis occurs. Contraindicated in pregnancy. |
| Fetal Monitoring |
■ FDA Black Box Warning
WARNING: VIRILIZATION IN WOMEN, PRECOCIOUS PUBERTY IN CHILDREN, AND HEPATOTOXICITY. Testosterone has been associated with hepatic adenomas and hepatocellular carcinoma.
| Serious Effects |
Known or suspected prostate cancer, male breast cancer, severe hepatic impairment, pregnancy, lactation.
| Precautions | Monitor for polycythemia, sleep apnea, cardiovascular risk, hypercalcemia in breast cancer patients, and potential for secondary exposure (virilization in children). |
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| Monitor maternal liver function, lipid profile, and hematocrit. Fetal ultrasound may be indicated if accidental exposure occurs; monitor for ambiguous genitalia. |
| Fertility Effects | Exogenous testosterone suppresses endogenous gonadotropin release, leading to oligospermia or azoospermia and reduced fertility in males. Effects may be reversible upon discontinuation. |