15.

Forest plot of network meta‐analysis of all trials for postoperative headache. Single drugs and combinations were compared with placebo (reference compound). RR = risk ratio, 95% CI = 95% confidence interval. RR < 1 favours the intervention, RR > 1 favours placebo. The blue lines indicate the range of equivalence (RR = 0.9 to 1.11). Treatments are ranked according to safety based on P scores. Abbreviations for treatments correspond to the first four letters of the drug name and are listed in the Methods and in Appendix 6.