Health Canada has issued a Notice of Compliance with conditions for memantine in the treatment of moderate to severe Alzheimer's disease (AD). The evidence of relative benefit and harm from memantine in this population derives from two randomized controlled trials (RCT) of 24 to 28 weeks' duration, in a total of 656 patients, and a post hoc subgroup analysis of 79 patients with severe AD from a third trial of 12 weeks. Memantine alone or in combination with donepezil demonstrates improvements in primary outcome scores of activities of daily living and cognition, but not of global performance. Memantine's rate of diffusion may be rapid, as it is the only drug available for severe AD and it has a potential for use in unapproved indications.