(2R,6R)-Hydroxynorketamine for the Treatment of Neuropathic Pain

The goal of this randomized double blind three way (1:1:1) cross over clinical trial is to evaluate the effectiveness and duration of analgesia of a single infusion of (2R,6R)-HNK 0.5mg/kg compared with ketamine 0.5mg/kg and saline with a 5-week interval between treatments on pain, pain qualities, physical function, pain interference, sleep disturbance and quality of life in subjects with neuropathic pain of the extremities. The questions that this study will address are: 1. What is the analgesic efficacy of (2R,6R)-HNK on pain intensity and pain qualities in patients with chronic (\>3 month) neuropathic pain (NP). 2. What will be the effective duration of a single infusion of (2R,6R)-HNK in patients with NP. 3. Will (2R,6R)-HNK reduce pain related effects including interference in daily activities of life, sleep disturbances and change the qualities of pain reported by patients. Participants will receive each of the three study drugs in a random order at 5-week intervals over a 15 week period. The drug will be administered as a 45-minute infusion. Participants will complete quantitative sensory and pain evaluations and complete patient reported pain outcomes prior to receiving the first study drug and at 7, 14 and 21 and 35 days following study drug administration.