The role of scopolamine administered via transdermal therapeutic systems in the prevention of postoperative vomiting, nausea, and nausea and vomiting is unclear. We performed a systematic search for full reports of randomized comparisons of transdermal scopolamine with inactive control. Dichotomous data were extracted. In the meta-analysis, relative risks and numbers-needed-to-treat/harm were calculated with 95% confidence intervals (CI). In 23 trials, 979 patients received transdermal scopolamine, and 984 patients received placebo. Sensitivity analyses were performed using restricted data for truncated control event rates (40%-80%) and for large trials. With these data, the relative risks for postoperative vomiting (five reports), nausea (five reports), nausea and vomiting (eight reports), and rescue treatment (three reports) were 0.69 (95% CI, 0.58-0.82), 0.69 (95% CI, 0.54-0.87), 0.76 (95% CI, 0.66-0.88), and 0.68 (95% CI, 0.54-0.85), respectively. This means that of 100 patients who receive transdermal scopolamine, approximately 17 will not experience postoperative vomiting who would have done so had they all received a placebo. However, 18 of 100 patients will have visual disturbances, eight will report dry mouth, two will report dizziness, one will be classified as being agitated, and 1-13 patients who are prescribed transdermal scopolamine will not use it correctly. The timing of application does not alter efficacy.
Implications: Of 100 patients who receive transdermal scopolamine, approximately 17 will not vomit in the postoperative period who would have done so had they all received a placebo. However, 18 of 100 patients will have visual disturbances, and eight will report dry mouth. Incorrect use further limits its efficacy.