Assessment of the Efficacy, Safety, and Tolerability of AVP-786 (Deudextromethorphan Hydrobromide [d6-DM]/Quinidine Sulfate [Q]) for the Treatment of Agitation in Patients With Dementia of the Alzheimer's Type

Inclusion Criteria: * Diagnosis of probable Alzheimer's Disease (AD) according to the 2011 National Institute on Aging-Alzheimer's Association (NIA-AA) working groups criteria * Participants with clinically significant, moderate/severe agitation at the time of screening and for at least 2 weeks prior to baseline that interferes with their daily routine and for which a prescription medication has been indicated, in the opinion of the investigator * The diagnosis of agitation must meet the provisional consensus definition of agitation in participants with cognitive disorders developed by the International Psychogeriatric Association (IPA) Agitation Definition Work Group. * A Clinical Global Impression of Severity of Illness scale for Agitation (CGIS-Agitation) score of ≥ 4 (moderately ill) at screening and baseline * Participants must have a reliable caregiver who is able and willing to comply with study procedures, including not administering any prohibited medications during the course of the study. * Caregiver who is able and willing to comply with all required study procedures. In order to qualify as a reliable informant (i.e., caregiver) capable of assessing changes in participant's condition during the study, the individual must spend a minimum of 2 hours per day for 4 days per week with the participant. Exclusion Criteria: * Participants with dementia predominantly of the non-Alzheimer's type (e.g., vascular dementia, frontotemporal dementia, Parkinson's disease, subs…