Opioid switching and variability in response in pain cancer patients.

Abstract

Opioid switching is a possible strategy for inadequate analgesia or unmanageable side effects. Its effectiveness ranges from 50 to 90% and is still debated. We analyzed the impact of opioid switching in a cancer pain population treated with strong opioids for pain. This is a post hoc analysis from a multicenter, randomized, four-arm, controlled, phase IV clinical trial. Outcome variables included the percentages of switches, the reasons for the switch, the dose changes before and after the switch, depending on the starting opioid, the response in case of inadequate analgesia, and unmanageable toxicity, and the variability of response among and within patients. We analyzed 498 patients. The opioid was switched in 79 patients (15.9%) 87 times, mainly for uncontrolled pain (52.3%), adverse opioid reactions (22.1%), both of these (4.8%), and dysphagia (20.8%). The reasons for switching varied depending on the starting opioid. Pain reduction was good after 51.45% of switches and control of opioid side effects was good after 43.5%. The relief of opioid-induced toxicity varied among adverse events and within each patient. The daily doses were higher after switching oral opioids and lower after transdermal drugs. Half of the patients who underwent switching experienced improved relief of pain or amelioration of opioid toxicity. The switch can help in the management of some cases but with many limits and uncertainties.