Clinical trial of a new oral contraceptive pill containing the natural oestrogen 17 beta-oestradiol.

The natural oestrogen, 17 beta-oestradiol, has been shown not to depress fibrinolysis and apparently has less influence on liver function and lipid metabolism than ethinyl oestradiol, the synthetic oestrogen in conventional 'combined' oral contraceptive tablets. A triple-blind study was therefore made of 215 women during 2051 treatment cycles with oral contraceptives containing either (i) 4 mg of micronized 17 beta-oestradiol and 3 mg norethisterone (Netagen 403), (ii) 4 mg 17 beta-oestradiol plus 2 mg of oestriol and 3 mg norethisterone (Netagen 423) or (iii) 50 microgram ethinyl oestradiol and 3 mg norethisterone (Netasyn). There were no pregnancies or thrombotic incidents. The numbers discontinuing treatment were about the same in the three groups, the main reasons being intermenstrual spotting in those on Netagen 423, amenorrhoea and weight gain in those on Netagen 403 and nausea and weight gain in those on Netasyn. The natural oestrogen showed promise as a new and safe component of the 'combined' pill.