Pharmacological treatment of cognitive deficits in Alzheimer's disease

To the Editor: The review by Brodaty and colleagues1 on drug treatment of Alzheimer's disease provides a good, concise and balanced overview. However, Pfizer takes issue with some of the referenced safety data.

In Box 3 of that article (Profiles of cholinesterase inhibitors), in reference to adverse effects of donepezil (Aricept, Pfizer), it is stated that "At 10 mg/day, nausea (17% of patients), diarrhoea (17%) and vomiting (10%) may occur.49" Reference 49 at this point appears to be an incorrect citation.

The figures of 17%, 17% and 10% for nausea, diarrhoea and vomiting, respectively, appear to have been taken from an article by Rogers and Friedhoff.2 It is important to note that this was a non-comparative, open-label extension study, and these incidences of gastrointestinal adverse events are inconsistent with data presented in the Australian Product Information for donepezil,3 which quote rates of nausea, diarrhoea and vomiting of 11%, 10% and 5%, respectively. These incidences are derived from a patient cohort of 1102 patents who participated in appropriately designed comparative (active and placebo) pre-registration studies of donepezil. These data have recently been confirmed in a one-year, randomised, placebo-controlled study of donepezil in patients with mild to moderate Alzheimer's disease.4 Incidences of 11.3%, 7.0% and less than 5% for nausea, diarrhoea and vomiting, respectively, are quoted in that study.

We contend that, while the citation referenced by Brodaty et al was incorrect, the figures quoted for the gastrointestinal safety incidences for donepezil are also inconsistent with the Product Information and current published data.