Dinges HC, Otto S, Stay DK, et al. - Researchers focused on the most common side effects rates, expressed as risk ratios (RRs), related to the use of different opioids for intravenous patient-controlled analgesia (PCA) in equianalgesic doses. They also intended to rank the substances accordingly. They selected 63 relevant randomized controlled trials from MEDLINE, EMBASE, the Cochrane Library (CENTRAL), and Web of Science. A significantly higher and a lower RR of nausea and vomiting was reported for buprenorphine and fentanyl, respectively. Lower risk of pruritus was reported for nalbuphine, butorphanol, methadone, and pethidine/meperidine. Significantly lower sedation scores resulted from the use of pethidine/meperidine, fentanyl, and oxymorphone. Significantly lower satisfaction scores were noted in relation to tramadol use, whereas significantly higher satisfaction scores were reported with oxycodone, alfentanil, remifentanil, fentanyl, and pethidine/meperidine. Experts concluded that, most likely, the incidence of pruritus and nausea/vomiting is slightly influenced by the opiate selected for treatment, although they found considerable differences in terms of better and worse opioids in the presented rankings. Concerning sedation and patient satisfaction, larger differences do exist between drugs, and selecting a suitable opioid may assist to improve PCA in this regard.