Objective: The aim of this double-blind, placebo-controlled study was to evaluate the effect of mefenamic acid and placebo on controlling irregular uterine bleeding secondary to Implanon use.
Design: Randomized placebo controlled trial.
Setting: Family Planning Clinic, King Chulalongkorn Memorial Hospital, Bangkok, Thailand.
Materials and methods: A total number of 50 Implanon users with irregular bleeding who attended the Family Planning Clinic at Chulalongkorn Memorial Hospital. These subjects were randomly allocated into two groups. Twenty-five users received mefenemic acid, 500 mg per oral three times a day for 5 days, and placebos were given to the rest of studied subjects in the similar manner. During the follow-up periods, the participants were requested to maintain their daily record of bleeding, spotting, and adverse effects. The days of bleeding and spotting and the percentage of bleeding stopped women were analyzed in week 1 and 4.
Results: The percentage of subjects in whom bleeding was stopped during week 1 after initial treatment was significantly higher in the mefenamic acid group than that of the placebo group (65.20%, 21.70%;p < 0.05). During the follow–up period (4 weeks after initial treatment ), a bleeding free-interval of >20 days was found in 56.50% of the subjects treated with mefenamic acid and 21.70% of those treated with placebo;
The mean number of bleeding/spotting days was lower in the group of patients with mefenamic acid treatment (10.52 and 16.78 days; p<0.05). The difference is statistically significant.
Conclusion: Mefenamic acid was more effective than placebo in short–term treatment of irregular bleeding and spotting associated with Implanon use.

Keywords: Bleeding-irregularities, Implanon implant, Mefenamic acid