CRD summary: This review evaluated the efficacy and safety of loperamide in the treatment of acute diarrhoea among children younger than 12 years. The authors concluded that children older than 3 years with minimal dehydration may benefit from loperamide administration. These conclusions have to be considered with some caution since they are based on relatively few studies and participants.

CRD commentary: This review addressed a well-defined question in terms of the participants, investigations, outcomes and study design. Several relevant databases were searched and attempts were made to identify unpublished articles, thereby reducing the potential for publication bias which was, however, not formally tested in the review. No language restrictions were applied, which reduces the possibility of language bias. The authors attempted to minimise bias and errors during the review process by carrying out the data extraction in duplicate. Since it is unclear whether the study selection and study quality assessment were also performed in duplicate, reviewer error and bias may have been introduced at these stages.

The authors stated that statistical heterogeneity was assessed, and that no statistical heterogeneity was found for the main outcome; this supports the authors' decision to pool the results in a meta-analysis. The statistical methods used in the meta-analysis were appropriate. A priori subgroup analyses were conducted to investigate interaction between treatment assignment and specific subgroups. However, the review itself may have been limited given the nature of the available evidence, as the authors acknowledged: for example, inconsistencies in outcome measures and issues with the reporting of serious adverse events. Furthermore, the strength of the authors' conclusions is weakened by the relatively low number of studies and patients included per outcome evaluated.