Ovarian activity in women taking an oral contraceptive containing 20 μg ethinyl estradiol and 150 μg desogestrel: Effects of low estrogen doses during the hormone-free interval,☆☆,,★★,

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Abstract

OBJECTIVE: We assessed the effect of low ethinyl estradiol doses given during the nominally hormone-free interval of the Mircette™ (brand of desogestrel/ethinyl estradiol and ethinyl estradiol) contraceptive regimen on ovarian activity.

STUDY DESIGN: In a randomized, double-blind study, healthy women received 150 μg desogestrel and 20 μg ethinyl estradiol for 21 days followed by either placebo for 7 days (Mircette™/placebo; N = 24) or placebo for 2 days and 10 μg ethinyl estradiol for 5 days (Mircette™/ethinyl estradiol; N = 23).

RESULTS: During cycles 2 and 3, the Mircette™/placebo group had a higher incidence of persistent ovarian follicles (eight subjects versus three subjects) and on average a greater maximum follicle diameter than the Mircette™/ethinyl estradiol group. One Mircette™/placebo subject probably ovulated in cycle 2, and another had a luteinized unruptured follicle; no such activity was seen in the in the Mircette™/ethinyl estradiol group. The study medication was well tolerated, and there were no apparent between-group differences in vaginal bleeding patterns.

CONCLUSION: The Mircette™ regimen, which includes low ethinyl estradiol doses during the hormone-free interval, more effectively suppresses ovarian follicular activity with a low monthly estrogen dose.

Section snippets

Study population

Healthy, sexually active women between 18 and 40 years old who were at risk for pregnancy and had normal ovulatory cycles (24 to 35 days) were considered for study participation. Additional entry requirements included body weight between 80% and 120% of ideal weight (according to 1983 Metropolitan Height and Weight Tables) (Build Study, 1979. Society of Actuaries and Association of Life Insurance Medical Directors of America 1980. Copyright 1983, Metropolitan Life Insurance Company), ability

Results

Of the 52 women recruited and randomly assigned to receive treatment, 47 subjects, 23 in the Mircette™/ethinyl estradiol group and 24 in the Mircette™/placebo group, received study medication. The treatment groups were comparable with respect to demographic, menstrual, and obstetric characteristics (Table II).

. Demographic, menstrual, and obstetric characteristics of the subjects

VariableMircette/EE (N = 23)Mircette/placebo (N = 24)
Age (yr)
 Mean27.527.9
 SD5.85.8
 Range18-3921-39
Weight (kg)
 Mean59.458.3

Comment

Despite the excellent efficacy of combined oral contraceptives, it is widely recognized that these agents do not produce complete ovarian suppression. Residual ovarian activity has been observed in women taking preparations that contain 50 μg ethinyl estradiol,7 and regimens that employ lower estrogen doses have been associated with less ovarian suppression than those with higher doses.4

Because of the low failure rate and the multiple antifertility effects of oral contraceptives, the clinical

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From the School of Medicine, University of Hull, Stepping Hill Hospital, and Tufts University School of Medicine.

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The study was conducted at Withington Hospital, Manchester, United Kingdom.

Financial support for this investigation was provided by NV Organon, Oss, The Netherlands.

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Reprint requests: S. R. Killick, MD, FRCOG, Professor of Reproductive Medicine, University of Hull, Princess Royal Hospital, Salthouse Rd., Kingston upon Hull, HU8 9HE United Kingdom.

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