Study designs
Each study utilized a single-dose, randomized, double-blind, active- and placebo-controlled crossover design to assess the abuse potential of esmethadone compared with oxycodone (Study 1—Oxycodone Study) or ketamine (Study 2—Ketamine Study) in healthy recreational drug users. All study drug administration and assessments were conducted in an inpatient setting. The overall design was consistent with FDA guidelines for assessing HAP [