THE PHARMACODYNAMIC EFFECTS OF AN ORAL-CONTRACEPTIVE CONTAINING 3-MG MICRONIZED 17-BETA-ESTRADIOL AND 0.150-MG DESOGESTREL FOR 21 DAYS, FOLLOWED BY 0.030-MG DESOGESTREL ONLY FOR 7 DAYS

During oral treatment with 3 mg micronized 17 beta-estradiol and 0.150 mg desogestrel for 21 days followed by 0.030 mg (A) desogestrel (15 w omen) or placebo (B) (14 women) for 7 days, ovarian function, bleeding pattern and estradiol levels were evaluated. The study was performed in a group-comparative, double-blind fashion. During a pre-treatment c ontrol cycle, using ultrasound scan, follicular diameter was measured on cycle days 10-16 and endometrial thickness on one of cycle days 22- 26. Estradiol was measured at the time of ultrasound scan and progeste rone three times in the luteal phase. During three treatment cycles, f ollicular diameter and endometrial thickness were monitored three time s weekly and at the same time, estradiol and progesterone were measure d. Treatment resulted in anovulation in all women. Maximum and mean es tradiol levels were approximately 900 pmol/l and 550 pmol/l during tre atment, respectively, and approximately 200 pmol/l during the estradio l-free weeks in both groups. Ten women showed ovarian activity (follic le size greater than or equal to 15 mm) during treatment, seven in gro up A and three in group B. Endometrial thickness decreased approximate ly 3 mm during treatment in both groups. The incidence of breakthrough bleeding and spotting was higher in group A when compared to group B. The study indicates that the combination of 3.0 mg micronized estradi ol and 0.150 mg desogestrel is an effective and safe contraceptive, of fering an acceptable cycle control. The addition of a low dose of deso gestrel during the pill-free period did not further suppress ovarian a ctivity nor improve the bleeding pattern. The results of this study sh ould be interpreted with great care, since the number of women studied is relatively small. (C) 1996 Elsevier Science Inc.