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).
Participants will be randomly assigned to either treatment or placebo group. The initial treatment phase will last for 4 weeks. At the end of the first 4 weeks, the treatment will be reversed after a 3 day washout period. During the 2nd intervention period, the study drug will be reversed (those receiving acetaminophen will receive the placebo drug and vice versa). The second treatment phase will last for 4 weeks. At the end of 2nd treatment phase, all study treatments will be discontinued
