The pharmacokinetic properties cypionate, estradiol valerate and benzoate, daily plasma levels of estradiol and estrone were evaluated in groups of 10, analyzed, 9 and 10 subjects in each case before and 3 weeks after the intramuscular administration of a single dose of 5.0 mg in 1.0 ml peanut oil. To minimize the contribution of endogenous estrogens on plasma levels, all subjects received a combined oral contraceptive levonorgestrel compound (150 micrograms) and ethinyl estradiol (30 micrograms) for three months before the study and during the period study. The administration of estradiol showed significantly lower peak levels of estradiol and estrone as the valerate and benzoate. Maximum plasma concentrations of estradiol and estrone were about 4 days after administration of estradiol valerate and benzoate and reached in a much shorter time (about 2 days) after administration of both. One hour after injection of the ester, the average percent increase in plasma levels of estradiol and estrone were significantly higher in the valerate and benzoate groups with respect to subjects who estradiol cypionate. The average duration of elevated estrogen level is the shortest in the benzoate group (4-5 days), followed by valerate (7-8 days) and cypionate (approximately 11 days). In any of the subjects studied increase of estradiol and / or estrone levels were found 2 weeks after injection of different esters. The data suggest that, of the three esters studied valerate offers the most predictable pharmacokinetics.
