The most effective and safe contraceptive method, intrauterine devices (IUDs), is still underutilized due to the pain barrier during IUD insertion. Lidocaine, a well-known local anesthetic, can be used to relieve IUD insertion pain. This study aimed at formulation, in vitro, in vivo and clinical evaluation of a novel lidocaine dual-responsive in situ gel. Pluronic and Gelrite® were used as thermosenstive and ion-activated polymers, respectively. In situ gels containing 2% lidocaine, pluronics and/or Gelrite® were prepared. The optimized dual-responsive formula (F 5) was clear, with 95% drug content, free flowing at room temperature and gel at vaginal temperature (T gel of 28 C). This optimized dual-responsive in situ gel was found to be superior to single-responsive one due to presence of Gelrite®, imparting resistance to dilution effect of simulated vaginal fluids. DSC thermograms revealed no interaction between …