Testosterone buciclate, a long-acting androgen ester, shows promise as a research agent for male hypogonadism.

Testosterone buciclate, administered intramuscularly (i.m.) at four different sites with 20 mg per site on the first and ninety-first days of a 360-day study period, demonstrates a decreased testicular volume between days 90 and 270, and significantly reduces sperm motility and gel penetrability, except on day 120, during days 45 to 240. It also leads to a reduction in sperm count from day 75 to 270 and increases the percentage of spermatozoa exhibiting cytoplasmic droplet retention and coiled tails, with the exception of day 120, throughout days 45 to 240[1].