TESTIM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TESTIM (TESTIM).
Testosterone replacement therapy; binds to and activates androgen receptors, modulating gene expression leading to male sexual development and maintenance of secondary sexual characteristics.
| Metabolism | Primarily hepatic via CYP3A4 and other CYPs; metabolites undergo glucuronidation and excretion in urine. |
| Excretion | Testosterone is primarily excreted in urine as glucuronide and sulfate conjugates (approximately 90%), with about 6% excreted in feces via bile. Less than 1% is excreted unchanged. |
| Half-life | Terminal elimination half-life of testosterone from serum is approximately 10-100 minutes after intravenous administration, but after transdermal application of Testim, the apparent half-life is longer (around 1-2 hours) due to continued absorption from the skin depot. The half-life of active metabolites (e.g., dihydrotestosterone) is about 2-3 hours. |
| Protein binding | Approximately 97-99% bound: mainly to sex hormone-binding globulin (SHBG) (about 40-50%) and albumin (about 50-60%), with a small fraction bound to corticosteroid-binding globulin. |
| Volume of Distribution | Volume of distribution (Vd) is approximately 1 L/kg, indicating extensive distribution into tissues. Pseudoequilibrium volume of distribution after transdermal application is about 28 L (for a 70 kg individual), suggesting significant partitioning into muscle and fat. |
| Bioavailability | Transdermal gel (Testim 1%): Approximately 10% of the applied dose is systemically absorbed; bioavailability is about 9-14% of the applied amount. Oral testosterone has negligible bioavailability (<1%) due to first-pass metabolism. |
| Onset of Action | Transdermal gel: Serum testosterone levels rise within 30 minutes of application, reaching therapeutic levels within 2-4 hours. Clinical effects (e.g., libido improvement) may be noticed within 1-2 weeks. |
| Duration of Action | Testim 1% gel applied once daily maintains serum testosterone within normal range for 24 hours with consistent daily application. Clinical effects persist throughout treatment duration; discontinuation leads to return of hypogonadal symptoms within weeks. |
| Molecular Weight | 288.42 |
Apply 5 g (1 tube) of 1% gel to clean, dry, intact skin of the shoulders, upper arms, or abdomen once daily, preferably in the morning. Dosage may be adjusted to 10 g (2 tubes) depending on clinical response. Apply immediately after opening and avoid bathing or swimming for at least 30 minutes.
| Dosage form | GEL |
| Renal impairment | No specific dose adjustment required for renal impairment. Use caution in severe renal impairment due to potential for reduced clearance of testosterone metabolites. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). In mild to moderate impairment (Child-Pugh class A or B), use with caution; start at lowest dose and monitor serum testosterone levels and hepatic function. |
| Pediatric use | Not indicated for use in pediatric patients under 18 years of age. Safety and efficacy have not been established. |
| Geriatric use | No specific dose adjustment recommended solely based on age. However, elderly patients may be more sensitive to androgenic effects; monitor for prostatic hypertrophy, edema, and sleep apnea. Consider lower initial doses (e.g., 5 g daily) and titrate based on clinical response and serum testosterone levels. |
| 1st trimester | Contraindicated: Testosterone is teratogenic, causing masculinization of female fetus. Risk of virilization of female genitalia if exposure occurs during first trimester. |
| 2nd trimester | Contraindicated: Continued risk of virilization of female fetus. Also associated with premature closure of epiphyseal plates and potential for decreased maternal milk production. |
| 3rd trimester | Contraindicated: Same risks as T2; additionally may cause premature labor or placental abruption. |
Clinical note
Comprehensive clinical and safety monograph for TESTIM (TESTIM).
| Placental transfer | Placental transfer documented; testosterone can cross placenta and cause virilization of female fetus. |
| Breastfeeding | Testosterone is excreted in breast milk. Can cause virilization in female infants and unknown effects on male infants. Avoid use while breastfeeding. |
■ FDA Black Box Warning
Testosterone has been associated with increased risk of cardiovascular events (myocardial infarction, stroke) and venous thromboembolism. Use with caution in patients with cardiovascular disease.
| Serious Effects |
PregnancyKnown or suspected prostate cancerKnown or suspected breast cancer in malesHypersensitivity to testosterone or any componentSevere urinary tract obstruction due to prostatic hypertrophy
| Precautions | Risk of cardiovascular events, venous thromboembolism, erythrocytosis, sleep apnea exacerbation, prostatic hypertrophy, and hepatotoxicity; monitor hematocrit and serum testosterone levels. |
| Food/Dietary | No specific food interactions. Grapefruit and grapefruit juice have no known interaction with testosterone gel. Avoid alcohol-based products on application sites as they may affect absorption. No dietary restrictions. |
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| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | Testosterone is classified as Pregnancy Category X. Use is contraindicated during pregnancy due to the risk of virilization of the female fetus, including clitoromegaly, labial fusion, and urogenital sinus abnormalities. Risks apply across all trimesters. |
| Fetal Monitoring | Monitor maternal blood pressure, lipid profile, hematocrit/hemoglobin, and liver function tests periodically. Perform pregnancy tests prior to initiation and during therapy if pregnancy is suspected. Assess fetal development via ultrasound if inadvertent exposure occurs. |
| Fertility Effects | Exogenous testosterone can suppress spermatogenesis by inhibiting FSH and LH, leading to reversible infertility in males. In females, adverse effects on ovarian function and fertility may occur due to hormonal imbalance. |
| Clinical Pearls | Apply Testim gel to clean, dry, intact skin on shoulders and upper arms. Avoid application to genital area or abdomen. Allow gel to dry before dressing. Wash hands thoroughly after application. Monitor serum testosterone levels 14 days after initiation. Avoid skin-to-skin contact with others until gel is dry. Testim may transfer to others via skin contact, causing unwanted androgen exposure. |
| Patient Advice | Apply Testim exactly as prescribed, once daily in the morning. · Do not apply to scrotum, penis, abdomen, or broken skin. · Let the gel dry completely before dressing or bathing. · Wash hands with soap and water after applying the gel. · Avoid direct skin contact with others (especially women and children) until the gel is dry. · Store at room temperature, away from heat and open flame. · Report signs of excessive testosterone (e.g., acne, hair loss, mood changes) to your doctor. · Testim is not for use in women or children. · Do not use if you have prostate or breast cancer. · Regular blood tests are needed to monitor testosterone levels and prostate health. |