A multicentred phase III comparative clinical trial of depot-medroxyprogesterone acetate given three-monthly at doses of 100mg or 150 mg: II. The comparison of bleeding patterns

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.