Efficacy of angiotensin II receptor antagonists in preventing headache: a systematic overview and meta-analysis

CRD COMMENTARY: The review question and the study selection criteria were clear. The literature search seems reasonably comprehensive, with sources additional to electronic databases being searched. However, it was unclear whether any language restrictions were applied, and the authors neglected to provide the dates over which the search was conducted. The authors did not provide information on whether, or how, validity assessments were carried out. The range of statistical tests employed seemed appropriate, but it was not mentioned whether publication bias was assessed. It was stated in the study objectives that a dose-response relationship was explored, but the results from this were not included in the study findings. Details of the different drug regimens were not supplied, apart from the stated use of losartan 50 mg as the baseline. A major limitation of the review is that it is entirely of studies in which AIIRAs were being used to treat hypertension, not headache. In such studies, the definition and reporting of headache are likely to have been inconsistent and incomplete. Therefore, any conclusions drawn about the effectiveness of AIIRAs in the treatment of headache can only be used as a basis for studies in the indication of interest.