Opioid switching is a therapeutic procedure used in pain management as a method to improve analgesic response and/or reduce adverse side effects. The rationale behind opioid substitution is the incomplete cross-tolerance between opioid. We report the case of an asian 51-year-old man with cancer pain unresponsive to oxycodone. In this case we hypothesize that the lack of response to oxycodone is linked to a phenomenon of pharmacokinetics tolerance.
