Approved & therapeutic
Testosterone enanthate
Xyosted
An injectable ester of testosterone approved in the United States for testosterone replacement in adult males, available as a generic intramuscular solution and as a once-weekly subcutaneous autoinjector. It is a Schedule III controlled substance.
- Status
- Testosterone enanthate is approved by the U.S. FDA and has official prescribing information.
- Evidence
- Approved labeling. Official prescribing information exists, based on clinical trials in people.
- Half-life
- Not stated as an ester half-life in the US labels. The generic label gives a half-life of 10 to 100 minutes for free testosterone itself; the enanthate ester is commonly reported in the human literature to release testosterone over roughly four to five days after intramuscular injection.
- How it's taken
- Intramuscular injection for the generic solution; subcutaneous injection into the abdominal region for the XYOSTED autoinjector, which must not be given intramuscularly or intravascularly.
- Mechanism
- Reproductive axis (GnRH / kisspeptin / oxytocin)
- Pathways
- Androgen
How Testosterone enanthate works
The enanthate ester is released from the injection depot and hydrolysed to testosterone, which acts on androgen receptors and is partly converted to estradiol and dihydrotestosterone. Exogenous androgen suppresses pituitary gonadotropin release, reducing endogenous testosterone production and spermatogenesis.
What research has looked at
- Labeled for testosterone replacement therapy in adult males for conditions associated with a deficiency or absence of endogenous testosterone, including primary hypogonadism and hypogonadotropic hypogonadism.
- The older intramuscular generic label additionally covers delayed puberty in carefully selected males and palliative treatment of metastatic breast cancer in certain postmenopausal women.
- The subcutaneous autoinjector carries an approved titration algorithm built on its registration pharmacokinetic and efficacy data: weekly dosing is adjusted against total testosterone trough concentration measured seven days after injection to hold patients inside a defined eugonadal target window.
Evidence level: Approved labeling. Official prescribing information exists, based on clinical trials in people. These are areas studied or reported, not promised effects.
Reported side effects and risks
- Contraindicated in men with carcinoma of the breast or known or suspected carcinoma of the prostate; in women who are or may become pregnant, because androgens cause virilization of the external genitalia of a female fetus; and in patients with a history of hypersensitivity to the product or any of its components (both the generic solution and the autoinjector are sesame oil based).
- Blood pressure increases; post-marketing ambulatory blood pressure monitoring studies confirmed a class-wide rise regardless of route. Baseline cardiovascular risk should be considered and blood pressure adequately controlled before starting, with periodic monitoring for new or worsening hypertension.
- Polycythemia and venous thromboembolism, including deep vein thrombosis and pulmonary embolism.
- Worsening of benign prostatic hyperplasia and potential risk of prostate cancer; adverse effects on spermatogenesis; gynecomastia; edema; sleep apnea; lipid changes; hypercalcemia.
- Risk of depression and suicide is listed in the Warnings and Precautions of the subcutaneous autoinjector label, alongside hepatic adverse effects including peliosis hepatis with prolonged high-dose use.
- Abuse of testosterone and dependence; a Schedule III controlled substance, with serum testosterone monitoring advised where abuse is suspected.
- Not for use in women outside the narrow oncologic indication. Women receiving androgens must be observed for virilization, including deepening of the voice, hirsutism, acne, clitoromegaly and menstrual irregularities; therapy must be stopped at the first evidence of mild virilism, because some virilizing changes are irreversible if treatment continues.
- In pediatric patients, androgens can accelerate bone maturation without a compensatory gain in linear growth and can cause premature closure of the epiphyses, permanently reducing adult height. The generic label directs monitoring of skeletal maturation every six months by X-ray of the hand and wrist.
- Androgens may decrease thyroxine-binding globulin, producing decreased total T4 and increased resin uptake of T3 and T4. Free thyroid hormone concentrations are unchanged and there is no clinical evidence of thyroid dysfunction, but thyroid panels can be misinterpreted during therapy.
- Limitation of use: safety and efficacy in age-related hypogonadism have not been established. The FDA class-wide testosterone labeling action of February 2025 explicitly retained this limitation, so treatment of age-related testosterone decline remains off-label.
- Not indicated or studied for athletic performance enhancement. Safety and efficacy in males under 18 years of age have not been established for the subcutaneous autoinjector.
Sources
- PubMed research on Testosterone enanthate · NIH · National Library of Medicine
- DrugBank record for Testosterone enanthate · DrugBank
- Active clinical trials for Testosterone enanthate · U.S. National Library of Medicine
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Testosterone enanthate FAQ
What is Testosterone enanthate?
An injectable ester of testosterone approved in the United States for testosterone replacement in adult males, available as a generic intramuscular solution and as a once-weekly subcutaneous autoinjector. It is a Schedule III controlled substance.
How does Testosterone enanthate work?
The enanthate ester is released from the injection depot and hydrolysed to testosterone, which acts on androgen receptors and is partly converted to estradiol and dihydrotestosterone. Exogenous androgen suppresses pituitary gonadotropin release, reducing endogenous testosterone production and spermatogenesis.
Is Testosterone enanthate FDA approved?
Yes. Testosterone enanthate is approved by the U.S. FDA and has official prescribing information. Evidence level: approved labeling. Official prescribing information exists, based on clinical trials in people.
What is the half-life of Testosterone enanthate?
Reported half-life: Not stated as an ester half-life in the US labels. The generic label gives a half-life of 10 to 100 minutes for free testosterone itself; the enanthate ester is commonly reported in the human literature to release testosterone over roughly four to five days after intramuscular injection.
How is Testosterone enanthate taken?
Intramuscular injection for the generic solution; subcutaneous injection into the abdominal region for the XYOSTED autoinjector, which must not be given intramuscularly or intravascularly.
What side effects have been reported with Testosterone enanthate?
Reported in the sources: Contraindicated in men with carcinoma of the breast or known or suspected carcinoma of the prostate; in women who are or may become pregnant, because androgens cause virilization of the external genitalia of a female fetus; and in patients with a history of hypersensitivity to the product or any of its components (both the generic solution and the autoinjector are sesame oil based); Blood pressure increases; post-marketing ambulatory blood pressure monitoring studies confirmed a class-wide rise regardless of route. Baseline cardiovascular risk should be considered and blood pressure adequately controlled before starting, with periodic monitoring for new or worsening hypertension; Polycythemia and venous thromboembolism, including deep vein thrombosis and pulmonary embolism; Worsening of benign prostatic hyperplasia and potential risk of prostate cancer; adverse effects on spermatogenesis; gynecomastia; edema; sleep apnea; lipid changes; hypercalcemia; Risk of depression and suicide is listed in the Warnings and Precautions of the subcutaneous autoinjector label, alongside hepatic adverse effects including peliosis hepatis with prolonged high-dose use; Abuse of testosterone and dependence; a Schedule III controlled substance, with serum testosterone monitoring advised where abuse is suspected; Not for use in women outside the narrow oncologic indication. Women receiving androgens must be observed for virilization, including deepening of the voice, hirsutism, acne, clitoromegaly and menstrual irregularities; therapy must be stopped at the first evidence of mild virilism, because some virilizing changes are irreversible if treatment continues; In pediatric patients, androgens can accelerate bone maturation without a compensatory gain in linear growth and can cause premature closure of the epiphyses, permanently reducing adult height. The generic label directs monitoring of skeletal maturation every six months by X-ray of the hand and wrist; Androgens may decrease thyroxine-binding globulin, producing decreased total T4 and increased resin uptake of T3 and T4. Free thyroid hormone concentrations are unchanged and there is no clinical evidence of thyroid dysfunction, but thyroid panels can be misinterpreted during therapy; Limitation of use: safety and efficacy in age-related hypogonadism have not been established. The FDA class-wide testosterone labeling action of February 2025 explicitly retained this limitation, so treatment of age-related testosterone decline remains off-label; Not indicated or studied for athletic performance enhancement. Safety and efficacy in males under 18 years of age have not been established for the subcutaneous autoinjector.
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