Opioids in neuropathic pain: clues from animal studies.

For many years the clinical consensus was that opioids were ineffective in neuropathic pain. However this view is changing and here we discuss the mechanisms of opioid analgesia in terms of the changes that can occur in preclinical models of nerve injury. We argue that opioid mechanisms can be perturbed by neuropathy but in most cases these negative influences can be overcome by dose-escalation.