Objective This study evaluated whether intramuscular (IM) ketamine is non‐inferior to intranasal (IN) esketamine for treatment‐resistant depression (TRD) and assessed differences in safety and healthcare costs. Methods In a retrospective, observational sequential cohort at the VA San Diego, 179 Veterans with TRD received eight treatments of either IN esketamine ( n = 89) or IM ketamine ( n =...