Enclomiphene citrate (designated as Androxal™) significantly increased natural levels of total and apparent free serum testosterone without increasing DHT proportionally. This new agent represents a new oral modality for elevating testosterone in men with secondary hypogonadism.
In a major clinical study, subjects at screening had low or borderline low (99–343 ng/dL) total serum testosterone levels with normal LH and FSH levels. On the first day of treatment, men in the study had total serum testosterone (TT) levels of 275 ± 88 ng/dL (mean ± SD).
After 14 days of treatment, there was a dose-dependent rise in T levels with enclomiphene: 12.5 mg per day was associated with a level of 412 ± 194 ng/dL; 25 mg per day with 520 ± 160 ng/dL, and 50 mg per day with 589 ± 172 ng/dL, values in the normal range (298 to 1034 ng/dL).
Enclomiphene represents the purified trans-isomer of clomi-phene citrate. Its primary advantage over clomiphene citrate is the absence of the estrogen agonist effects of the cis-isomer, zuclomi- phene. Enclomiphene citrate (the trans– or (E)-isomer) has effects consistent with estrogen antagonism.