Efficacy and safety of Wuling capsule for insomnia disorder: a systematic review and meta-analysis of randomized controlled trials

Objectives: Wuling capsule has been used in treatment of insomnia disorder in China for decades, but the reported treatment efficacy of different studies was not consistent. This study intended to evaluate the efficacy and safety of Wuling capsule for insomnia disorder, so as to provide evidence for clinical application. Methods: Eight databases (MEDLINE, EMBASE, Ovid, Cochrane Library, Chinese National Knowledge Infrastructure, VIP information database, Chinese Biomedical Database and Wanfang) were searched from inception to September 14, 2021. Randomized controlled trials (RCTs) comparing Wuling capsule with controls in adults with insomnia disorder were eligible. The primary outcome was sleep quality assessed by Pittsburgh Sleep Quality Index (PSQI), and the secondary outcomes were severity of insomnia disorder measured by Sleep Dysfunction Rating Scale (SDRS) and adverse events. This study was conducted according to the Cochrane Handbook for Systematic Reviews of Interventions version 5.1.0. Results: Nineteen RCTs with a total of 1850 participants were included. In terms of sleep quality assessed by PSQI, Wuling capsule significantly lowered PSQI score (MD:-1.92, 95% CI: [-2.34,-1.50], P < 0.00001, I-2 = 95%) compared to controls, and the effect of Wuling capsule was significantly better than control no matter when Wuling capsule as monotherapy (MD:-1.71, 95% CI: [-2.33,-1.09], P < 0.00001, I-2 = 97%) or as adjunctive therapy (MD:-2.10, 95% CI: [-2.66,-1.55], P < 0.00001, I-2 = 90%). Wuling capsule was more effective for the treatment duration lasted 8 weeks (MD:-2.57, 95% CI: [-3.52,-1.62], P < 0.00001, I-2 = 93%) than 4 weeks (MD:-1.68, 95% CI: [-2.13,-1.22], P < 0.00001, I-2 = 95%). In terms of severity of insomnia disorder measured by SDRS, Wuling capsule significantly reduced SDRS score (MD:-4.21, 95% CI: [-4.95,-3.46], P < 0.00001, I-2 = 0%) compared to benzodiazepines. Wuling capsule significantly reduced adverse events compared to controls (RR: 0.47, 95% CI: [0.34, 0.65], P < 0.00001, I-2 = 43%). Conclusion: Wuling capsule can safely and effectively improve sleep quality in patients with insomnia disorder. However, these findings require careful recommendation due to the high heterogeneity and high risk of bias in the included trials. Clinical trials with higher quality designs are needed. (c) 2022 The Authors. Published by Elsevier B.V.