Pharmacological control of opioid-induced pruritus: a quantitative systematic review of randomized trials.

BACKGROUND AND OBJECTIVE Numerous drugs have been used to prevent or to treat opioid-induced pruritus in the surgical setting. Their relative efficacy is not well understood. METHODS The methods employed involved the systematic search (MEDLINE, EMBASE, Cochrane library, bibliographies, without language restriction, up to June 2000) for full reports of randomized comparisons of any intervention which is thought to be anti-pruritic (active) compared with placebo or no treatment (control) in surgical (including labour) patients receiving opioids. The number of patients who had no pruritus were analysed using relative risk and number-needed-to-treat with 95% confidence interval. RESULTS Twenty-two trials (1477 patients) were analysed. Two trials (66 patients), both with low-dose propofol, were on treatment of established pruritus; propofol had no anti-pruritic effect compared with Intralipid. In prophylaxis trials, the average incidence of pruritus with control was 59% (range, 10% to 100%). Most mu-receptor antagonists were efficacious: intravenous naloxone 0.25-2.4 microg kg-1 h-1, relative risk 2.31 (95% confidence interval, 1.5 to 3.54), number-needed-to-treat to prevent pruritus compared with control 3.5; oral naltrexone 9 mg, relative risk 2.80 (1.35-5.80), number-needed-to-treat 1.7; naltrexone 6 mg was less effective and 3 mg did not work; different intravenous and epidural nalbuphine regimens, relative risk 1.71 (1.12-2.62), number-needed-to-treat 4.2. Intravenous nalmefene 0.5 or 1 mg was not anti-pruritic. Intravenous (but not epidural) droperidol 2.5 mg was efficacious, relative risk, 1.71 (1.28-2.29), number-needed-to-treat 4.9. There was a lack of evidence for any anti-pruritic efficacy with prophylactic propofol, epidural or intrathecal epinephrine, epidural clonidine, epidural prednisone, intravenous ondansetron, or intramuscular hydroxyzine. CONCLUSION Naloxone, naltrexone, nalbuphine and droperidol are efficacious in the prevention of opioid-induced pruritus; minimal effective doses remain unknown. There is a lack of valid data on the efficacy of interventions for the treatment of established pruritus.