Does a single intravenous injection of the 5HT3 receptor antagonist ondansetron have an analgesic effect in neuropathic pain? A double-blinded, placebo-controlled cross-over study.

Author(s): McCleane GJ, Suzuki R, Dickenson AH

Affiliation(s): Rampark Pain Centre, Lurgan, Northern Ireland. gary@mccleane.freeserve.co.uk

Publication date & source: 2003-11, Anesth Analg., 97(5):1474-8.

Publication type: Clinical Trial; Randomized Controlled Trial

Neurokinin-1-expressing neurones in lamina I to III of the spinal cord are intimately involved in the regulation of ascending and spino-bulbal pathways that regulate excitatory transmission. In experimental animals, ablation of these neurones reduces the responses to a variety of nociceptive stimuli. Furthermore, in animals, spinal application of the selective 5HT3 receptor antagonist ondansetron mimics these effects, indicating that 5HT3 receptors play a pronociceptive role and mediate descending excitatory controls that allow spinal neurones to fully code peripheral stimuli. In this study, we examined the potential analgesic effect of a single IV injection of ondansetron in humans with chronic neuropathic pain. Each consenting subject received a single IV injection of 8 mg ondansetron and placebo in varying order at least 1 wk apart with pain scores being recorded for the 48 h preceding and after each injection. Pain scores were significantly reduced 2 h after ondansetron injection (but at no other time point). This suggests that ondansetron can have an analgesic effect in neuropathic pain. Side effects were minor and infrequent. IMPLICATIONS: The selective 5HT3 receptor antagonist ondansetron, currently used as an antiemetic, may also have analgesic properties. Side effects with a single IV injection are infrequent and usually mild.