Prospective randomized double-blind trial of the correlation between time of administration and antiestrogenic effects of clomiphene citrate on reproductive end organs

To investigate whether the timing of administration of clomiphene citrate (CC) affects hormone levels, follicular recruitment, reproductive end organs, and pregnancy rates.

Prospective, randomized, double-blind trial.

Academic center. PATIENT(S): Twenty-three patients with unexplained infertility. INTERVENTION(S): Twenty-three patients with unexplained infertility underwent 45 cycles of CC and IUI. For each cycle, patients were randomized either to receive 100 mg of CC on days 1-5 and placebo on days 5-9 (study group), or placebo on days 1-5 and CC on days 5-9 (control group). MAIN OUTCOME MEASURE(S): The difference in uterine artery PI, number of follicles, endometrial thickness, and pregnancy rates. RESULT(S): Gonadotropins and E2 levels, as well as uterine artery pulsatility index, were significantly higher in the study group on day 5. In addition, in the study group, a longer time interval existed between finishing CC and IUI (8 versus 6 days; MD = 2 days; 95% CI = 1-3) and the pregnancy rate was higher than in the control group (6 versus 0; OR = 15.1; 95% CI = 1.1-72.4). CONCLUSION(S): Clomiphene citrate commenced on day 1 of the menstrual cycle, rather than day 5, results in more rapid follicular growth, a longer CC-free period before IUI, and higher pregnancy rates. Although methodologically sound, our results should be taken with some degree of caution because they are based on a relatively small number of patients.