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. |
| Molecular Weight | 288.42 |
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 | Testosterone is contraindicated in pregnancy; there are no adequate studies in pregnant women. Animal studies show fetal masculinization and adverse effects. |
| 2nd trimester | Testosterone is contraindicated in pregnancy; may cause virilization of female fetus. |
| 3rd trimester | Testosterone is contraindicated in pregnancy; may cause virilization of female fetus. |
Clinical note
Comprehensive clinical and safety monograph for TESTRED (TESTRED).
| Placental transfer | Testosterone crosses the placenta; can cause virilization of female fetuses. Data from animal studies and case reports confirm transfer. |
| Breastfeeding | Testosterone is excreted in human milk; may cause virilization in female infants and accelerated growth in male infants. Avoid breastfeeding during therapy and for at least 1 month after last dose. |
■ 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 |
PregnancyKnown or suspected carcinoma of the breast in womenKnown or suspected carcinoma of the prostate in menHypersensitivity to testosterone or any componentWomen with hypercalcemia (due to metastatic breast cancer)
| Precautions | Monitor for polycythemia, sleep apnea, cardiovascular risk, hypercalcemia in breast cancer patients, and potential for secondary exposure (virilization in children). |
| Food/Dietary | No significant food interactions. Avoid excessive alcohol consumption as it may increase risk of hepatotoxicity. Grapefruit juice does not interact significantly. Maintain a balanced diet to support overall health during androgen therapy. |
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| Lactation Rating | L4 (possibly hazardous) |
| 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 | 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. |
| Clinical Pearls | Monitor for signs of virilization in women and precocious puberty in children. Measure serum testosterone levels periodically to ensure therapeutic range and avoid supraphysiologic levels. Assess liver function tests, lipid profile, and hematocrit/hemoglobin at baseline and periodically. Use with caution in patients with known or suspected prostate cancer or breast cancer. Avoid in men with severe lower urinary tract symptoms due to benign prostatic hyperplasia. Intramuscular injections should be given deep into the gluteal muscle to minimize injection site reactions. |
| Patient Advice | Take exactly as prescribed; do not change dose or frequency without consulting your doctor. · Report any signs of virilization (e.g., deepened voice, facial hair growth, acne) or unusual changes in mood, sleep, or libido. · For transdermal formulations, apply to clean, dry skin on the back, abdomen, or thighs; rotate sites to avoid irritation. · Do not use in women who are or may become pregnant; can cause harm to the fetus. · Keep out of reach of children; store at room temperature away from moisture and heat. · Inform your doctor of all other medications, including over-the-counter, vitamins, and herbal supplements. · Regular blood tests are required to monitor safety and effectiveness. |