In elderly patients oxybutynin (Sigma-Aldrich) is commonly used to treat overactive bladder despite increased prevalence of Alzheimer's disease in this population. We determined whether oxybutynin altered plaque formation, amyloid beta peptide expression and behavior in a transgenic mouse model of Alzheimer's disease expressing the mutant human presenilin 1 (deltaE9) and a chimeric mouse/human amyloid precursor protein (APPswe).