Men's Osteoporosis Support Group

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Long Acting Testosterone Undecanoate

J Urol. 2008 Oct 16. [Epub ahead of print], Long Acting Testosterone Undecanoate Therapy in Men With Hypogonadism: Results of a Pharmacokinetic Clinical Study. Morgentaler A and others. PMID: 18930255. This study tested the efficacy of intramuscular (IM) injections of long acting testosterone undecanoate in 116 males with hypogonadism. Each subject received 750 mg of testosterone undecanoate at the start of the study, and at week 4 and 14. Serum testosterone levels were tested multiple times up to 70 days. Serum testosterone levels remained in a normal range for over 90% of the participants throughout the study. There were small increases in hematocrit, hemoglobin and PSA during the study. No prostate cancer or gynecomastia were detected during the study. The authors concluded, "This 24-week clinical study demonstrated that 750 mg testosterone undecanoate depot injection administered intramuscularly at 0, 4 and 14 weeks achieves serum testosterone levels in the normal range during a 10-week dosing interval."

Editor's comments: I first wrote about this long-term injectable testosterone in a July 2000 Newsletter. Information at the manufacturer's website indicates that this medication is very near to receiving FDA approval. It is made by Indevus Pharmaceuticals, Inc., with the drug name of NEBIDO(R). So keep checking online search engines or the Indevus website if you would like to get this form of testosterone for your hypogonadism.

In a 2007 review article in Clin Interv Aging by Yassin AA and Haffejee M, the authors note, "After 2 initial injections with a 6-week interval, the following intervals between two injections are almost always 12-weeks, amounting eventually to a total of 4 injections per year." [Bold text is by the editor]. Four yearly injections to maintain normal serum testosterone levels is quite an improvement over previous IM dosing regimens. These comments may have been made about a higher dose that had been approved in Europe, so the 750 mg dose may require more than four yearly injections. The FDA approval information should be helpful to explain that better. Often twice monthly, or more frequent injections, had been required with the cypionate testosterone that is used currently.

There are other pharmacological methods for treating hypogonadism, including patches and gels. I have personally used the 5 mg Androderm patch for several years now with no problems and have found it quite pleasant not to need injections. But going back to only four per year would certainly be a huge improvement, if needed. For more on this topic see this Update.

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