[Central and peripheral actions of an oral contraceptive with reduced oestrogen content (author's transl)]

The action spectrum of an oral contraceptive which contained a reduced amount of the oestrogen component (0.04 mg ethinyl-oestradiol and 2.0 mg lynoestrenol) was investigated in 4 volunteer subjects. Serum levels of LH, 17 beta-oestradiol and progesterone were determined by radioimmunoassay and, in addition, the karyopyknotic index and cervical function were studied daily from the 8th day of the cycle. These parameters were determined in a control cycle, in the cycle during administration of the oral contraceptive and in the subsequent treatment-free cycle. Furthermore, the bleeding patterns were studied in 284 treatment cycles of 26 patients. Results of these studies indicate complete contraceptive protection by inhibition of ovulation and by an efficient cervical barrier action already during the first treatment cycle. Withdrawal bleeding was observed 3 to 4 days after ingestion of the last tablet. Spotting was recorded in 11 subjects during the first treatment cycle but was rarely observed during further treatment. Blood loss and bleeding control is comparable to that of other combined oral contraceptives with reduced oestrogen content.