Triphasic Randomized Clinical Trial: comparative frequency of intermenstrual bleeding

Oral contraceptives have the highest theoretic efficacy of all reversible forms of contraception, yet in practice they have an actual failure rate equivalent to that of some barrier methods. The efficacy of oral contraceptives depends primarily on patient compliance. So-called "nuisance" side effects, such as intermenstrual bleeding (breakthrough bleeding or spotting), play a major role in their discontinuation. The Triphasic Randomized Clinical Trial compared the incidence of these side effects in three groups of subjects taking NET (A) (Ortho-Novum 7/7/7), LNG (Tri-Levlen), or NET (B) (Tri-Norinyl). Subjects taking NET (A) had the highest incidence of intermenstrual bleeding (63%) followed by NET (B) (44%) and LNG (33%). Only the difference between NET (A) and LNG attained statistical significance (p less than 0.030). Control subjects had no breakthrough bleeding and a 4% incidence of spotting. Further research is warranted to establish the cause of the disparity in the incidence of intermenstrual bleeding among patient groups assigned to the three oral triphasic contraceptives.