Targeted pharmacotherapy of evoked phenomena in neuropathic pain: a review of the current evidence

Abstract

OBJECTIVE: Evoked phenomena in clinical neuropathic pain are viewed as a window into the underlying pathophysiology. They are also potential therapeutic targets. This study sought evidence for the effect on such evoked phenomena of currently used agents. DESIGN: We reviewed MEDLINE (1966-2006) and EMBASE (1980-2006) to locate all randomized, double-blind, placebo-controlled trials examining therapeutic responses of evoked neuropathic pain phenomena, including dynamic mechanical allodynia, pin prick hyperalgesia, and thermal allodynia. We also noted the methods of elicitation of these evoked pain phenomena. RESULTS: We found 40 articles meeting our inclusion criteria. A wide variety of methods was used to evoke neuropathic pain phenomena. For dynamic mechanical allodynia, there is some evidence for the efficacy of ketamine, alfentanil, and morphine, but only when administered intravenously. For other agents and other evoked pain phenomena, there is insufficient evidence to draw firm conclusions. CONCLUSIONS: There is minimal evidence to guide clinicians in treating evoked pain phenomena in clinical neuropathic pain states. There is little clinical evidence to either support or refute theoretical arguments for efficacy of specific agents in evoked neuropathic pain phenomena. More and larger trials are needed to examine these phenomena. Consensus is required with respect to methods used to elicit these evoked phenomena.