Peripherally restricted kappa opioid agonists have been developed to target kappa opioid receptors located on visceral and somatic afferent nerves for relief of inflammatory, visceral, and neuropathic chronic pain. The recently shown efficacy of these analgesics—combined with a possible lower abuse potential and side effect burden than mu opioid receptor agonists—makes delta and peripherally restricted kappa opioid receptor agonists promising targets for treating pain.1
