Maher DP, et al. – The authors performed this study to investigate whether chronic opioid therapy modifies quantitative sensory testing (QST) changes following ketamine infusion in chronic pain patients. The outcomes demonstrated that in QST phenotypes, low dose ketamine infusions produced subtle changes that were modified by the chronic use of opioids. In the setting of chronic opioid use, this showed the potential diagnostic and therapeutic value of ketamine.