Testosterone enanthate
Testosterone enanthate is an esterified variant of testosterone that comes as an injectable compound with a slow-release rate.  This slow release is achieved by the presence of the enanthate ester functional group attached to the testosterone molecule. This testosterone derivative was first approved on December 24, 1953.  In 2017, about 6.5 million retail prescriptions for testosterone therapy were filled. The majority of the prescriptions written were for injectable (66%) and topical (32%) testosterone products. As recent as 1 October 2018, the US FDA approved Antares Pharma Inc.'s Xyosted - a subcutaneous testosterone enanthate product for once-weekly, at-home self-administration with an easy-to-use, single dose, disposable autoinjector. As the first subcutaneous autoinjector product designed for testosterone replacement therapy, this innovative formulation removes transfer concerns commonly associated with testosterone gels and potentially reduces the need for in-office/in-clinic injection procedures that may inconvenience patients with frequent visits to the clinic.