Multinational comparative clinical evaluation of two long-acting injectable contraceptive steroids: norethisterone oenanthate and medroxyprogesterone acetate: 2. bleeding patterns and side effects.
A WHO sponsored comparative trail (9 centers) studied the bleeding patterns and side effects experienced by 1678 women using injectable (every 12 weeks) norethisterone enanthate (NOR) and depot-medroxyprogesterone (DMPA). 388.8 women-years of menstrual experience with NOR and 372.5 with DMPA were studied. The percentage of women with total amenorrhea with DMPA was significantly higher than with NOR for all injection intervals. The porportion of women with total amenorrhea increased significantly over time with both drugs (chi-square=33.9 for NOR and 73.4 for DMPA; P < .001). After 1 year, 35% of DMPA and 8.6% of NOR users had total amenorrhea. With NOR, the cycle length distribution changed markedly over time, with the percentage of short cycles under 25 days diminishing as the percentage of long cycles in excess of 46 days increased. In contrast, DMPA held cycle length patterns more or less constant. Length of bleeding and spotting episodes were significantly greater with DMPA. The mean number of bleeding/spotting days decreased over time with both drugs; the difference from the 1st to 4th injection was statistically significant (P < .001). Though the overwhelming majority of women experienced abnormal cycles with both drugs, the percentage of normal cycles remained fairly constant during consecutive intervals. Headache was the most frequently reported complaint: 10.7% of DMPA and 6.9% of NOR users. Other nonmenstrual side effects were reported with similar frequencies in both groups.