Published online by Cambridge University Press: 31 July 2008
Chlormadinone acetate (0·5 mg) was given continuously to 200 patients for 1512 cycles in an investigation lasting a little over 2 years. Only a small number of the women stayed in the trial for the whole period. The women were in the reproductive age group and of proved fertility. Lack of cycle control was the chief drawback. However, the majority of the cycles were of normal duration, intensity and flow. Breakthrough bleeding occurred in 3·8% of the total cycles. Of the patients 49% had side effects in 18·6% of the cycles. They were common in the first 3 months but were mild. No pregnancy occurred due to method failure. Six pregnancies occurred due to tablet omission on 2 or more days. A heavy drop-out rate of 78·5% was found. The majority of the patients who dropped out did so for reasons not related to the drug; only 14% of the patients dropped out due to side effects. Vaginal cytohormonal study, premenstrual endometrial biopsies and postcoital tests were carried out during the trial to study the mode of action of the drug.