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A multicentered phase III clinical trial was conducted in seven countries to compare two dosages of depot-medroxyprogesterone acetate (DMPA), 100mg and 150mg, given every 90 days. Contraceptive efficacy and side-effects of both regimens were reported previously. Their effect on vaginal bleeding patterns is the object of this paper. A total of 1216 women were randomly assigned to a dose group and 1156 of them provided a menstrual diary. The comparison of the bleeding patterns is made using a 90-day reference period approach and following the guidelines published by WHO. In addition, the longest bleeding/spotting episode and the longest bleeding/spotting-free interval are calculated over the entire diary length. The only difference found between the two dose groups is a higher incidence of amenorrhea with the 150mg regimen. Overall, there is a high degree of consistency between the reasons given by individual women for discontinuing the contraceptive method and their vaginal bleeding pattern during the 90 days preceding discontinuation. However the data revealed large between-centre differences, both in the incidence of specific patterns, and in the identification by women of bleeding problems as reasons for discontinuation. This last point suggests that the life-table analysis underestimates the true incidence of menstrual irregularities. Comments on the reference period analysis method are made.

Two dosages of depot-medroxyprogesterone acetate (DMPA), 100 mg and 150 mg given every 90 days, were compared in two groups of women with regard to effectiveness, reported complaints and reasons for discontinuation. A total of 1216 women were recruited into a seven-centre, multinational, randomized clinical trial. Follow-up was for a period of one year and resulted in a total of 5507 woman-months of experience of 100 mg DMPA and 5429 woman-months of experience of the 150 mg dose. The study showed little difference in efficacy and side effects between the two treatment groups. Two pregnancies occurred in women receiving 100 mg DMPA giving a Pearl Index of 0.44 per 100 woman-years. None occurred in the 150 mg group. There was no difference in the overall continuation rates between the two groups at one year, being 59.3% in the 100 mg group and 58.8% in the 150 mg group. Except for discontinuation of method use for amenorrhea, the rates of all medical and non-medical reasons given for discontinuation were comparable between the two treatment groups. Women's perception of lack of bleeding was reported as amenorrhea and resulted in discontinuation rates at 12 months for amenorrhea of 7.2% for women receiving 100 mg of DMPA and 12.5% for those receiving the 150 mg dose. Three centres, Alexandria, Karachi and Szeged, made the major contributions to this difference.