Intrauterine Mepivacaine Instillation vs Placebo for Pain During IUD Placement

Importance: Concern about pain during intrauterine device (IUD) placement is common and reduces selection of an IUD. Reducing procedure-related pain may support informed contraceptive decision-making and patient autonomy and has also been associated with improved patient satisfaction and procedural experience. Objective: To determine whether intrauterine instillation of mepivacaine reduces pain during IUD placement in nulliparous individuals. Design, Setting, and Participants: Multicenter, double-blind, randomized, placebo-controlled trial conducted at 11 outpatient gynecology, maternal health, and youth clinics in Sweden from May 2021 through June 2024. Nulliparous individuals aged 18 to 31 years opting for IUDs with smaller-diameter placement tubes (levonorgestrel 19.5 mg, 13.5 mg, or copper IUD) were eligible. Key exclusion criteria included ongoing pregnancy, IUD replacement, pelvic infection, and allergy to local anesthetics. A total of 370 participants were randomized. Interventions: Participants were randomly assigned (1:1) (185 per group) to intrauterine instillation of 10 mL of mepivacaine (20 mg/mL) or sodium chloride (9 mg/mL) via a hydrosonography catheter 2 minutes before IUD placement. Participants, clinicians, and outcome assessors were blinded to treatment allocation. Main Outcomes and Measures: The primary outcome was clinician-adjusted difference in pain scores during IUD placement, measured on a 100-mm visual analog scale. The primary analysis included all randomized participants with available primary outcome data. Prespecified secondary analyses included tolerability and overall experience. Results: A total of 370 participants were randomized. Mean age was 21.7 (SD, 3.0) years in the mepivacaine group and 21.7 (SD, 2.9) years in the placebo group. Mean pain score during IUD placement was 43.8 mm (SD, 24.7) in the mepivacaine group and 58.6 mm (SD, 21.5) in the placebo group (mean difference, 14.8 mm [95% CI, 10.0-19.6]; P < .001). Adjustment for individual clinician yielded similar results (mean difference, 14.2 mm [95% CI, 9.7-18.6]; P < .001). Tolerable pain was reported by 172 of 175 participants (98.3%) in the mepivacaine group and 159 of 174 (91.4%) in the placebo group (relative risk, 1.08 [95% CI, 1.02-1.13]; NNT, 15 [95% CI, 9-43]). Conclusions and Relevance: Intrauterine instillation of 10 mL of mepivacaine (20 mg/mL) significantly reduced pain and improved tolerability during IUD placement compared with instillation of placebo saline. Trial Registration: EudraCT Identifier: 2020-002271-36.