[Ovarian activity, cycle behavior and tolerance of low dosage oral contraceptives: a comparative study]

In a double-blind randomized study, the suppression of ovarian activity, the effects on the cervix and endometrium, menstrual bleeding patterns and overall tolerance were assessed during administration of two low-dose oral contraceptives (20 micrograms ethinylestradiol EE, 500 micrograms norethisterone--Eve 20, Grünenthal, Aachen; 20 micrograms EE, 150 micrograms Desogestrel--Lovelle, Organon, Munich), 118 healthy women (ages: 18 to 35 years) with comparable bioprofiles (height, weight, menstrual cycle patterns) were studied in 10 investigation centres during medication with either Eve 20 (n = 59) or Lovelle (n = 59). During 3 treatment cycles, ovarian activity was evaluated by sonographic determination of follicular size and by simultaneous assessment of serum endocrine profiles (gonadotropins LH and FSH, ovarian steroids estradiol [E2] and progesterone [P]). Treatment cycles 4 to 6 served to evaluate the patterns of menstrual bleeding and the overall subjective tolerance on each contraceptive. While on the preparations, no ovarian activity (as judged by a lack of follicular growth and suppressed sex steroid levels) was found in over 90% of all investigated cycles. Follicular activity and/or cyst formation were detected in 18 of 173 cycles (Eve 20) and in 5 of 175 cycles (Lovelle) respectively. Gonadotropin levels were suppressed (LH < 6 IU/l, FSH < 8 IU/l) in most treatment cycles (Eve 20: 76.6% vs. Lovelle: 84.8%). Serum E2 concentrations exceeding 0.1 nmol/l indicated residual follicular activity in 19.3% (Eve 20) vs. 12.2% (Lovelle) of all cycles. As estimated by serum P levels over 5 nmol/l, ovulation had presumably occurred in 4.1% (Eve 20) vs. 2.9% (Lovelle) of treatments respectively. However, when the sonographic and endocrinological data were combined, no ovulation was documented in any treatment cycle. In addition, the quality of the cervical mucus was minimal and a low endometrial thickness was found in the majority of women, indicating strong progestogen effects of both contraceptives. Menstrual irregularities (intermenstrual spotting, break-through bleeding) occurred initially on each preparation, but were mostly resolved when the pills were continued. The acceptance of each investigated drug was rated as very good or good by most subjects. These observations allow us to conclude that the rate of ovarian suppression with inhibition of follicular activity is high under low-dose oral contraceptives. The different progestogens as components of these contraceptive pills display equally good anti-conceptive effects on both the cervix and the endometrium. Furthermore, the rate of irregular menstrual bleeding is acceptable for these low-dose contraceptives. The high acceptance of each preparation suggests that such agents will have a high rate of acceptability in clinical use.