This is a Phase 3, multicenter, randomized, double-blind, active-controlled study in approximately 160 subjects undergoing primary unilateral TKA under spinal anesthesia. The study will have 2 cohorts, enrolling in parallel.~Cohort 1 -PK, PD, Efficacy, and Safety, Cohort 2 -Efficacy and Safety~An adaptive study design will be used in this study. An interim analysis to evaluate the sample size assumptions and evaluate futility will occur when a total of approximately 80 subjects (40 subjects in each arm) combined from either Cohort 1 or Cohort 2 have enrolled and provided complete assessment data for the primary efficacy outcome.~The time from study drug administration until the end of participation is POD 14 (±3 days). Therefore, subjects may participate in the study for up to 62 days.
The purpose of the study is to compare magnitude of postsurgical analgesic effect in different groups following a single dose of study drug when administered via adductor canal block in subjects undergoing primary unilateral total knee arthroplasty.