STUDIES ON LOW-DOSE ORAL-CONTRACEPTIVES - PLASMA-HORMONE CHANGES IN RELATION TO DELIBERATE PILL (MICROGYNON-30) OMISSION

The effects of deliberate Microgynon 30 (150 .mu.g levonorgestrel (NG) + 30 .mu.g 17.alpha.-ethinylestradiol (EE2)) pill omission upon the circulating plasma levels of LH [lutropin], FSH [follitropin], estradiol-17 .beta. (E2) and progesterone [P] were studied in the early and later part of the course of pills. Daily blood samples were obtained from 3 women on days 17-24 of a course of treatment during which the pill was deliberately missed on day 19 of treatment. Daily blood samples were obtained from a further 7 subjects from the day preceding commencement of treatment for 8 consecutive days, i.e., up to day 7 of treatment; in this instance the pill was missed on day 4 of treatment. Specific radioimmunoassay methods were used to determine LH, FSH, E2, P, NG and EE2 levels in all plasma samples. In a previous study using Microgynon 30, an accidental omission of a pill on day 12 coincided with a sharp rise of FSH in the blood and near zero titers of the synthetic steroids; the present study did not confirm this. Blood levels of FSH measured at the time of pill omission in both early and late phases of the treatment course did not show any marked rise. Cervical mucus examined in 6 of the volunteers displayed physical characteristics associated with an uninterrupted ancillary contraceptive effect. These observations together with the maintained suppression of LH, E2 and P, demonstrated that Microgynon 30 remained an effective contraceptive in the subjects studied even when single pill omission had taken place after the 4th day of the course of tablets.