This thesis provides a comprehensive review of cholinesterase inhibitors (ChEIs) in mild-to-moderate Alzheimer's disease, focusing on efficacy and long-term safety. It reviews key clinical trials involving donepezil, rivastigmine, and galantamine, analyzing their impact on cognitive function, global clinical status and daily living activities, while also discussing potential long-term safety concerns. The findings indicate that ChEIs provide modest but sustained symptomatic benefits, particularly when initiated early and maintained over time. Long-term safety and tolerability data suggest that cholinesterase inhibitors are generally well-tolerated with gastrointestinal side effects being the most common. Overall, it supports the continued use of ChEIs as a core pharmacologic strategy in mild to moderate Alzheimer's disease care.