Comparison studies of cholinesterase inhibitors for Alzheimer's disease

There is uncertainty about which of the three available cholinesterase inhibitors should be prescribed as initial therapy for patients with Alzheimer's disease. We have assessed the reports of three trials that directly compared cholinesterase inhibitors. They were reviewed for sponsorship, authorship, main results, proportions of individuals who achieved maximum daily doses of the study cholinesterase inhibitors, and how the studies dealt with items on the CONSORT checklist for randomised controlled trials. All studies were funded by pharmaceutical companies, coauthored by their employees, and reported results that favoured the sponsor's product. In two studies, a significantly lower proportion of people achieved the target maximum daily dose for the comparator drug than for the sponsor's product. Between 27% and 55% of CONSORT items per study were rated as inadequately reported. The methodological limitations of these studies reduce our confidence in the validity of the conclusions drawn in the published reports.