Abstract

Memantine is an uncompetitive N-methyl-d-aspartate receptor antagonist and probably also has an indirect dopaminergic action at high concentrations. We describe a person with Alzheimer's disease who developed chorea and dystonia after inadvertently doubling of her daily dose by taking extended-release (XR) memantine twice daily, rather than once daily (planned dose memantine XR, 21 mg once daily), after the drug was switched from immediate release (IR, 10 mg twice daily). Memantine is rarely associated with movement disorders, but this case emphasises the need for awareness of potential problems when switching from memantine IR to XR.