Evaluation of an ultra-low-dose oral contraceptive for dysmenorrhea: a placebo-controlled, double-blind, randomized trial.

OBJECTIVE: To evaluate the efficacy and safety of an ultra-low-dose oral contraceptive (NPC-01; 0.02 mg ethinyl estradiol and 1 mg norethisterone) in subjects with dysmenorrhea.

DESIGN: Placebo-controlled, double-blind, randomized trial.

SETTING: Clinical trial sites.

PATIENT(S): Two hundred fifteen subjects with dysmenorrhea.

INTERVENTION(S): Subjects were randomly assigned to receive NPC-01, placebo, or IKH-01 (0.035 mg ethinyl estradiol and 1 mg norethisterone) for four cycles.

MAIN OUTCOME MEASURE(S): Total dysmenorrhea score (verbal rating scale) assessing pain on the basis of limited ability to work and need for analgesics.

RESULT(S): The reductions of total dysmenorrhea score and visual analog scale score after the treatment were significantly higher in the NPC-01 group than in the placebo group. Furthermore, the efficacy of NPC-01 was comparable to that of IKH-01. The overall incidence of side effects was significantly higher in the NPC-01 group than in the placebo group. All side effects that occurred in the NPC-01 group were previously reported in patients receiving IKH-01. No serious side effects occurred.

CONCLUSION(S): The ultra-low-dose contraceptive NPC-01 relieved dysmenorrhea as effectively as IKH-01. Thus, NPC-01 could represent a new option for long-term treatment of dysmenorrhea.

CLINICAL TRIAL IDENTIFICATION NUMBER: NCT01129102.