Testosterone depot injection in male hypogonadism: a critical appraisal

Testosterone compounds have been available for almost 70 years, but the pharmaceutical formulations have been less than ideal. Traditionally, injectable testosterone esters have been used for treatment, but they generate supranormal testosterone levels shortly after the 2- to 3-weekly injection interval and then testosterone levels decline very rapidly, becoming subnormal in the days before the next injection. The rapid fluctuations in plasma testosterone are subjectively experienced as disagreeable. Testosterone undecanoate is a new injectable testosterone preparation with a considerably better pharmacokinetic profile. 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. Plasma testosterone levels with this preparation are nearly always in the range of normal men, so are its metabolic products estradiol and dihydrotestosterone. The "roller coaster" effects of traditional parenteral testosterone injections are not apparent. It reverses the effects of hypogonadism on bone and muscle and metabolic parameters and on sexual functions. Its safety profile is excellent due to the continuous normalcy of plasma testosterone levels. No polycythemia has been observed, and no adverse effects on lipid profiles. Prostate safety parameters are well within reference limits. There was no impairment of uroflow. Testosterone undecanoate is a valuable contribution to the treatment options of androgen deficiency.