Modulation of Remifentanil-Induced Analgesia, Hyperalgesia, and Tolerance by Small-Dose Ketamine in Humans

Abstract

Coadministration of ketamine and morphine for pain relief is still controversial. Our experimental pain study with volunteers showed that ketamine enhances opioid analgesia without increasing sedation and reduces respiratory depression. Opioid-induced hyperalgesia and tolerance were not affected by ketamine and depended on the type of nociceptive stimulus. This may explain the conflicting results on opioid tolerance in previous studies.