PubMed2002
Side effects caused by oral contraceptives discourage compliance with and continuation of oral contraceptives. A suggested disadvantage of biphasic oral contraceptive pills compared to triphasic oral contraceptive pills is an increase in breakthrough bleeding. We examined this potential disadvantage by conducting a systematic review comparing biphasic oral contraceptives with triphasic oral contraceptives in terms of efficacy, cycle control, and discontinuation because of side effects. We included randomized, controlled trials comparing any biphasic oral contraceptive with any triphasic oral contraceptive when used to prevent pregnancy. Only two trials of limited quality met our inclusion criteria. Larranaga compared two biphasic and one triphasic pills, each containing levonorgestrel and ethinyl estradiol. No important differences emerged, and the frequency of discontinuation because of medical problems was similar with all three pills. Percival-Smith compared a biphasic pill containing norethindrone (Ortho 10/11) with a triphasic pill containing levonorgestrel (Triphasil) and another triphasic pill containing norethindrone (Ortho 7/7/7). The biphasic pill had inferior cycle control compared with the levonorgestrel triphasic pill. The available evidence is limited and of poor quality; the internal validity of these trials is questionable. Given that caveat, the biphasic pill containing norethindrone was associated with inferior cycle control compared with the triphasic pill containing levonorgestrel. This suggests that the choice of progestin may be more important that the phasic regimen in determining bleeding patterns.