Effect of prophylactic 5-HT3 receptor antagonists on pruritus induced by neuraxial opioids: a quantitative systematic review

Pruritus is a frequent adverse event observed after neuraxial administration of opioids. Central 5-hydroxytryptamine subtype 3 (5-HT3) receptors may be activated in this process. This systematic review aimed to evaluate the efficacy of prophylactic 5-HT3 receptor antagonists on neuraxial opioid-induced pruritus. We searched Medline, Embase, and Cochrane Collaboration Library databases. Studies were evaluated with the Oxford Validity Scale. Studies with a score of 3 or more and reporting prophylactic administration of 5-HT3 receptor antagonists vs placebo were included. Fifteen randomized double-blind controlled trials (n=1337) were selected. 5-HT3 antagonists (n=775) significantly reduced pruritus odds ratio (OR) 0.44 (95% confidence interval, 95% CI, 0.29-0.68), P=0.0002, number-needed-to-treat (NNT) 6 (95% CI, 4-14)], the treatment request for pruritus OR 0.58 (95% CI, 0.43-0.78), P=0.0003, NNT 10 (95% CI, 7-20)], the intensity of pruritus weighted mean difference (WMD) -0.35 (95% CI, -0.59 to -0.10), P=0.007], the incidence and the intensity of postoperative nausea and vomiting (PONV), and the need of rescue treatment respectively, Peto odds ratio (Peto OR) 0.43 (95% CI, 0.31-0.58), P<0.00001, NNT 7 (95% CI, 6-10); WMD -0.12 (95% CI, -0.24 to 0.00), P=0.05 and OR 0.42 (95% CI, 0.20-0.86), P=0.02, NNT 8 (95% CI, 5-35)]. However, the funnel plot was asymmetric, suggesting a risk of publication bias. 5-HT3 receptor antagonists may be an effective strategy in preventing neuraxial opioid-induced pruritus and PONV. Further large randomized controlled trials are required to confirm these findings.