CRD Summary: Clonidine improved the duration of analgesia and anaesthesia when used as an adjunct to intermediate-acting local anaesthetics for some peripheral nerve blocks. The authors' conclusions reflected the evidence presented, but in light of both a lack of reporting, and the presence of several methodological concerns with the review, the authors' conclusions may not be reliable.

CRD Commentary: The review addressed a clear research question and was supported by adequate inclusion criteria. The search strategy was adequate, but it was limited to published studies in English. The review was therefore subject to the possibility of publication and language bias, which means that relevant studies may have been missed. Study selection was performed independently by two reviewers, which minimised the risk of reviewer error and bias, but details were not provided on methods used in the data extraction process. Although the authors stated that only double blind RCTs were eligible for inclusion in the review, there was no formal validity assessment, which means the reliability of the evidence presented was unclear. A narrative synthesis was appropriate given the diversity of the included trials. However, there was often a lack of information about the comparator treatments used, making it difficult to interpret results. Interpretation was further restricted by the authors only presenting very basic result details. The authors' conclusions reflected the evidence presented, but in light of both a lack of reporting, and the presence of several methodological concerns with the review, the authors' conclusions may not be reliable.