Opioid rotation in the management of chronic pain: where is the evidence?

The management of chronic pain remains a challenge because of its complexity and unpredictable response to pharmacological treatment. In addition, accurate pain management may be hindered by the prejudice of physicians and patients that strong opioids, classified as step 3 medications in the World Health Organization ladder for cancer pain management, are reserved for the end stage of life. Recent information indicates the potential value of strong opioids in the treatment of chronic nonmalignant pain. There are, up until now, insufficient data to provide indications about which opioid to use to initiate treatment or the dose to be used for any specific pain syndrome. The strong inter-patient variability in opioid receptor response and in the pharmacokinetic and pharmacodynamic behavior of strong opioids justifies an individual selection of the appropriate opioid and stepwise dose titration. Clinical experience shows that switching from one opioid to another may optimize pain control while maintaining an acceptable side effect profile or even improving the side effects. This treatment strategy, described as opioid rotation or switch, requires a dose calculation for the newly started opioid. Currently, conversion tables and equianalgesic doses are available. However, those recommendations are often based on data derived from studies designed to evaluate acute pain relief, and sometimes on single dose studies, which reduces this information to the level of an indication. In daily practice, the clinician needs to titrate the optimal dose during the opioid rotation from a reduced calculated dose, based on the clinical response of the patient. Further research and studies are needed to optimize the equianalgesic dosing tables.