Pharmacokinetics
Testosterone undecanoate has a very long elimination half-life and mean residence time when given as a depot intramuscular injection. Its elimination half-life is 20.9 days and its mean residence time is 34.9 days in tea seed oil, while its elimination half-life is 33.9 days and its mean residence time is 36.0 days in castor oil. These values are substantially longer than those of testosterone enanthate (which, in castor oil, has values of 4.5 days and 8.5 days, respectively). Testosterone undecanoate is administered via intramuscular injection once every three months or so. Chemistry
Testosterone undecanoate, or testosterone 17β-undecanoate, is a synthetic androstane steroid and a derivative of testosterone. It is an androgen ester; specifically, it is the C17β undecylate (undecanoate) ester of testosterone. A related testosterone ester with a similarly very long duration is testosterone buciclate. History
In the late 1970s, testosterone undecanoate was introduced for oral use in Europe, although intramuscular testosterone undecanoate had already been in use in China for several years. Intramuscular testosterone undecanoate was not introduced in Europe and the United States until much later, in the early to mid 2000s and 2014, respectively. Testosterone undecanoate was approved in the United States after three previous rejections due to safety concerns. Society and culture
Generic names
Testosterone undecanoate is the generic name of the drug and its USAN and BAN. It is also referred to as testosterone undecylate.
In DPB, the nodules are more restricted to the respiratory bronchioles, while in OB they are often found in the membranous bronchioles (the initial non-cartilaginous section of the bronchiole, that divides from the tertiary bronchus) up to the secondary bronchus. OB is a bronchiolar disease with worldwide prevalence, while DPB has more localized prevalence, predominantly in Japan. Prior to clinical recognition of DPB in recent years, it was often misdiagnosed as bronchiectasia, COPD, IPF, phthisis miliaris, sarcoidosis or alveolar cell carcinoma. Treatment
Macrolide antibiotics, such as erythromycin, are an effective treatment for DPB when taken regularly over an extended period of time. Clarithromycin or roxithromycin are also commonly used. The successful results of macrolides in DPB and similar lung diseases stems from managing certain symptoms through immunomodulation (adjusting the immune response), which can be achieved by taking the antibiotics in low doses. Treatment consists of daily oral administration of erythromycin for two to three years, an extended period that has been shown to dramatically improve the effects of DPB. This is apparent when an individual undergoing treatment for DPB, among a number of disease-related remission criteria, has a normal neutrophil count detected in BAL fluid, and blood gas (an arterial blood test that measures the amount of oxygen and carbon dioxide in the blood) readings show that free oxygen in the blood is within the normal range. Allowing a temporary break from erythromycin therapy in these instances has been suggested, to reduce the formation of macrolide-resistant P. aeruginosa.