Cycle control on low-dose oral contraceptives: a comparative trial.
Cycle control was studied comparing the monophasic oral contraceptive Loestrin with three low-dose phasic preparations (Triphasil, Ortho 10/11 and Ortho 7/7/7) in 391 women of whom 300 completed 6 cycles. Loestrin subjects had a rate of occurrence (31% of cycles) for intermenstrual bleeding (IMB) comparable to the rates for subjects on the phasic preparations (36%, 37% and 37%, respectively). Triphasil subjects had lower rates than the Ortho 10/11 and Ortho 7/7/7 subjects (p less than 0.01) in cycle one when all subjects were analyzed and in pre-study users when continuing menstrual flow (CMF) episodes were not included as IMB. IMB was a cause for dropping out of the study in 7% of subjects who were evenly distributed between groups. There were no differences between groups for BTB when perceived by subjects as a side effect. Spotting was perceived as a side effect more often with Ortho 10/11 and Ortho 7/7/7 use than with Triphasil (p less than 0.01). Loestrin, Ortho 10/11 and Ortho 7/7/7 subjects were more likely to report amenorrhea (p less than 0.001) and less likely to report leg cramps (p less than 0.01) compared to those on Triphasil. Triphasil subjects were less likely to report acne than subjects on Ortho 7/7/7 (p less than 0.01).
Conclusions are limited by the identification of only one trial, the methodological shortcomings of that trial, and the absence of data on accidental pregnancies. However, the trial found no important differences in bleeding patterns between the biphasic and monophasic preparations studied. Since no clear rationale exists for biphasic pills and since extensive evidence is available for monophasic pills, the latter are preferred.