A Cochrane review [Abstract] 1 included 12 studies with a total of 9 591 subjects.
As compared to progestin-only injectable contraceptives, combination injectable contraceptives including either depot medroxyprogesterone acetate (DMPA) 25 mg plus estradiol cypionate (E2C) 5 mg (4 trials, 1 128 women) or norethisterone enanthate (NET-EN) 50 mg plus estradiol valerate (E2V) 5 mg (1 trial, 1112 women), resulted in lower rates of early study discontinuation due to amenorrhea or other bleeding problems, but had higher rates of overall discontinuation and discontinuation due to other reasons than the progestin-only comparison contraceptives. Acceptability results favored the combination injectable in one study and the progestin-only in another.
Studies comparing two combination injectable contraceptives found that NET-EN 50 mg plus E2V 5 mg resulted in less overall discontinuation and less discontinuation due to amenorrhea or prolonged bleeding than DMPA 25 mg plus E2C 5 mg (5 trials, 7187 women). However, these differences were not detected in all trials. The NET-EN plus E2V group also had more cyclical (regular) bleeding and fewer prolonged bleeding reference periods than the DMPA plus E2C group. The groups did not differ in their amenorrhea rates.
Authors' comment: While discontinuation rates can be viewed as a measure of method acceptability, the findings should be interpreted with caution since discontinuation rates are dependent on many other factors.
Comment: The quality of evidence is downgraded by study quality (inadequate or unclear allocation concealment and lack of blinding).
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