CRD Summary: The authors concluded that the use of paracetamol (acetaminophen) at commonly prescribed dosages is associated with small or no increased risk for upper gastrointestinal complications. The conclusions were in line with the evidence presented. However, the inclusion of only observational studies and lack of an assessment of validity make it difficult to be certain of the reliability of the authors' conclusions.

CRD Commentary: This review addressed a clearly defined question and was supported by clearly stated inclusion and exclusion criteria for the study design, intervention and outcome. The search involved one electronic database, so it is possible that relevant studies could have been missed. It is not clear if any language restrictions were applied and there were no attempts to search for unpublished literature. Publication bias was assessed. More than one author contributed to the study selection process, thereby reducing the risk of errors and bias, but other aspects of review methodology were not reported. No validity assessment was performed, thus it is difficult to assess the comprehensiveness and validity of the literature presented. Data about the participants in the included studies were limited, which makes it difficult to assess the generalisability of the review findings.

The methods used to pool the studies were appropriate and statistical heterogeneity was tested. Subgroup analyses were conducted to explore the gradient dose-effect, but the small group of studies included limits the evidence. The authors' conclusions appear to be supported by the evidence; however, the lack of an assessment of the validity of the included studies, and their observational design, makes it difficult to confirm these conclusions.