Intrauterine mepivacaine instillation for pain relief during intrauterine device insertion in nulliparous women: a double-blind, randomized, controlled trial

Abstract

ObjectiveTo evaluate whether intrauterine mepivacaine instillation before intrauterine device (IUD) insertion decreases pain compared to placebo. Study designWe performed a double-blind, randomized, controlled trial comparing mepivacaine 1% 10 mL versus 0.9% NaCl intrauterine instillation using a hydrosonography catheter 5 min before IUD insertion in women 18 years of age or older. Participants completed a series of 10-cm visual analogue scales (VAS) to report pain during the procedure. The primary outcome was the difference in VAS scores with IUD insertion between intervention group and placebo. Secondary outcomes included VAS before and after insertion and analgesia method acceptability. ResultsWe randomized 86 women in a 1:1 ratio; both groups had similar baseline characteristics. In the intention-to-treat analysis, the primary outcome, median VAS with IUD insertion, was 4.8 cm in the intervention group [n=41, interquartile range (IQR) =3.1–5.8] and 5.9 cm in the placebo group (n=40, IQR=3.3–7.5, p=.062). In the per-protocol analysis, the median VAS with IUD insertion was 4.8 cm (IQR=3.1–5.5) and 6.0 cm (IQR=3.4–7.6) for the intervention and placebo groups, respectively (p=.033). More women in the intervention group reported the procedure as easier than expected (n=26, 63.4% vs. n=15, 37.5%), and fewer reported it as worse than expected (n=3, 7.3% vs. n=14, 35%, p=.006). ConclusionIntrauterine mepivacaine instillation before IUD insertion modestly reduces pain, but the effect size may be clinically significant. Implications statementWhile the reduction in VAS pain scores did not meet our a priori difference of 1.3 points for clinical significance, participants' favorable subjective reaction suggests that this approach merits further study.