Kyzatrex

Testosterone undecanoate is a long-chain fatty acid ester of testosterone and a Schedule III controlled substance. FDA-approved products include oral capsules (Jatenzo, Tlando and Kyzatrex) and an intramuscular depot injection (Aveed, 750 mg/3 mL in castor oil with benzyl benzoate). Lake Hills Pharmacy dispenses Kyzatrex as a manufactured product; it is not compounded.

FDA-labeled indication (oral and intramuscular products): testosterone replacement therapy in adult males with conditions associated with a deficiency or absence of endogenous testosterone, either primary hypogonadism (congenital or acquired) or hypogonadotropic hypogonadism (congenital or acquired).

Limitations of use: oral labels state safety and efficacy are not established in age-related hypogonadism. Aveed is reserved for patients in whom benefits outweigh the risk of pulmonary oil microembolism and anaphylaxis.

Testosterone undecanoate has no FDA-labeled use in women; prescribers who treat women with testosterone generally use other low-dose forms (see Warnings & Precautions).

Testosterone undecanoate is a prodrug hydrolyzed to testosterone, which binds the androgen receptor directly and after 5-alpha-reduction to dihydrotestosterone, and is aromatized to estradiol. These actions maintain male secondary sex characteristics, spermatogenesis, muscle, bone and erythropoiesis.

Oral: the lipophilic ester is absorbed largely through the intestinal lymphatics, partly bypassing hepatic first-pass metabolism; absorption depends on dietary fat, so capsules are taken with food, once or twice daily per label.

Intramuscular: the oil depot releases the ester slowly, allowing a dosing interval of about 10 weeks per the Aveed label.

Testosterone is bound to SHBG and albumin, metabolized in the liver and excreted mainly in urine as conjugates.

• Men with breast cancer or known or suspected prostate cancer.
• Pregnancy.
• Known hypersensitivity to the product or its ingredients (for Aveed, including castor oil and benzyl benzoate).

• Blood pressure: testosterone can raise blood pressure; FDA class labeling (2025) adds this warning to all testosterone products and adds results of the TRAVERSE cardiovascular safety trial. Oral testosterone undecanoate can increase blood pressure, which can raise the risk of major adverse cardiovascular events over time; it is not recommended in patients with uncontrolled hypertension, and blood pressure should be monitored.
• Polycythemia: hematocrit can rise; interrupt therapy if it exceeds label thresholds.
• Venous thromboembolism: DVT and pulmonary embolism have been reported, including in patients without polycythemia.
• Prostate: worsening of benign prostatic hyperplasia and possible increased risk of prostate cancer; evaluate before and during therapy.
• Abuse and dependence: supraphysiologic misuse is linked to serious cardiovascular and psychiatric events; withdrawal can occur.
• Reduced spermatogenesis and testicular atrophy at higher doses; may impair fertility.
• Edema, with or without heart failure, in patients with cardiac, renal or hepatic disease; gynecomastia; sleep apnea, especially with risk factors; lipid changes; hypercalcemia in patients with cancer and bone metastases; decreased thyroxine-binding globulin.
• Pediatric use: androgens can accelerate bone maturation without matching linear growth.

Women: no testosterone product is FDA-labeled for androgen replacement or sexual desire concerns in women. Prescribers use compounded testosterone in women at doses far below male doses, targeting the premenopausal female range. Cautions include virilization (acne, hirsutism, scalp hair loss, voice deepening and clitoral enlargement, which may be permanent), lipid changes, and excluding pregnancy.

• Insulin and oral antidiabetic drugs: androgens can lower blood glucose; dose reduction of the antidiabetic drug may be needed.
• Warfarin and other oral anticoagulants: androgens can increase anticoagulant effect; monitor INR more often when starting or stopping testosterone.
• Corticosteroids and ACTH: additive fluid retention; use caution in cardiac, renal or hepatic disease.
• Laboratory tests: androgens lower thyroxine-binding globulin, so total T4 falls while free thyroid hormone is unchanged.
• Oral products: use caution with other drugs that raise blood pressure.

Oral: hypertension, increased hematocrit, headache, nausea, diarrhea, dyspepsia, acne, peripheral edema and increased PSA. Intramuscular: injection-site pain, acne, increased PSA, fatigue and mood changes, plus the reactions in the boxed warning. In women, androgen excess causes virilization.

Testosterone is contraindicated in pregnancy. Exposure can virilize a female fetus. Pregnancy should be excluded before women start testosterone, and women of reproductive potential should use reliable contraception per prescriber guidance.

Lactation: testosterone use is not recommended while breastfeeding because of potential adverse effects in the infant. Male fertility: high doses suppress spermatogenesis, which may be prolonged.

• Serum testosterone at the timing the product label specifies, after starting and after dose changes.
• Hematocrit at baseline, during the first months of therapy and periodically.
• Blood pressure at baseline and periodically.
• PSA and prostate assessment in men, per guideline and patient age; lipids; symptoms of sleep apnea, edema and venous thromboembolism.
• In women: serum testosterone, signs of virilization, lipids, and pregnancy status.
• Aveed: observe for 30 minutes after each injection for pulmonary oil microembolism and anaphylaxis.

• Kyzatrex (testosterone undecanoate) capsules Prescribing Information.
• Jatenzo (testosterone undecanoate) capsules Prescribing Information.
• Aveed (testosterone undecanoate) injection Prescribing Information.
• Endocrine Society Clinical Practice Guideline: Testosterone Therapy in Men with Hypogonadism (2018).
• Global Consensus Position Statement on the Use of Testosterone Therapy for Women (2019).