The research study will investigate if routine analgesic use will reduce behavioral expressions of dementia and pain in older adults with Alzheimer's disease or other dementias. Using a randomized, placebo-controlled, double-blind, cross-over design, the investigators will compare effects of a routine acetaminophen intervention (650 mg administered routinely by mouth three times per day for 4 weeks) to those of routine placebo (methylcellulose), also given for 4 weeks. The maximum dose to be administered will be 1,950 mg per 24 hours, which is below the current FDA recommendations (maximum dose of 3,000 mg/day).