This is a Phase 3, 38-week, randomized, double-blind, placebo-controlled, multicenter, outpatient study in subjects with psychosis associated with Alzheimer's Disease. The primary objective of the study is to evaluate relapse prevention in subjects with psychosis associated with Alzheimer's Disease treated with KarXT compared to placebo. The secondary objectives of the study are to evaluate the time from randomization to discontinuation for any reason or relapse and safety and tolerability in subjects with psychosis associated with Alzheimer's Disease treated with KarXT compared to placebo.