Testosterone undecanoate

Testosterone undecanoate (USAN, BAN) (brand names Aveed, Andriol, Androxon, Cernos Depot, Nebido, Panteston, Restandol, Nebido-R, Reandron 1000, Undestor), or testosterone undecylate, is an androgen and anabolic steroid and a testosterone ester. It is used in androgen replacement therapy primarily for the treatment of male hypogonadism, and has also been investigated for use as a male contraceptive or as hormone replacement therapy in transgender men. Unlike other testosterone esters, testosterone undecanoate is available in both oral and intramuscular formulations. The Reandron 1000 formulation (Nebido in the United States) contains 1000 mg of testosterone undecanoate suspended in castor oil with benzyl benzoate for solubilisation and as a preservative, and is administered by intramuscular injection. As an excipient, benzyl benzoate has been reported as a cause of anaphylaxis in a case in Australia. Bayer includes this report in information for health professionals and recommends that physicians "should be aware of the potential for serious allergic reactions" to preparations of this type. In Australia, reports to ADRAC, which evaluates reports of adverse drug reactions for the Therapeutic Goods Administration, show several reports of allergic issues since the anaphylaxis case from 2011.

Testosterone undecanoate has a very long elimination half-life and mean residence time when given as a depot intramuscular injection. The elimination half-life and mean residence time of testosterone undecanoate are 2.5-fold and 4-fold longer than those of testosterone enanthate (the values for testosterone enanthate being 4.5 days and 8.5 days, respectively).

Aveed brand testosterone undecanoate was approved for use in the United States by the FDA in 2014, after three previous rejections due to safety concerns. It is administered at a dosage of 1,000 mg every 12 weeks via intramuscular injection. In addition to parenteral, an oral formulation of testosterone undecanoate (brand name Andriol) is also available in Europe, but must be taken two or three times a day in combination with food.