Testosterone enanthate injection USP, provides testosterone enanthate, a derivative of the primary endogenous androgen testosterone, for intramuscular administration. In their active form, androgens have a 17-beta-hydroxy group. Esterification of the 17-beta-hydroxy group increases the duration of action of testosterone; hydrolysis to free testosterone occurs in vivo. Testosterone esters are less polar than free testosterone. Testosterone esters in oil injected intramuscularly are absorbed slowly from the lipid phase; thus Testosterone Enanthate can be given at intervals of two to four weeks. Testosterone enanthate used in males to treat primary hypogonadism (congenital or acquired) – testicular failure due to cryptorchidism, bilateral torsion, orchitis, vanishing testis syndrome, or orchidectomy. In females: metastatic mammary cancer. Other methods of counteracting estrogen activity in cases of adrenalectomy, hypophysectomy, and/or antiestrogen therapy.