Alzheimer’s disease is a chronic, progressive, neurodegenerative disorder of the brain characterized by deficits in memory and cognitive function. Donepezil is a reversible, noncompetitive cholinesterase inhibitor. It has a high binding specificity for brain acetylcholinesterase, with little to no affinity for butyrylcholinesterase. It is approved by the FDA for the treatment of severe Alzheimer’s disease. The aim of this work is to formulate depot injection lipospheres and in situ implants containing Donepezil for treatment of Alzheimer disease in order to decrease dosing frequency and increase patient compliance. The work is divided into: Chapter 1: Formulation and In Vitro Evaluation of Injectable Donepezil Lipospheres. Chapter 2: Formulation and In Vitro Evaluation of Injectable Donepezil in Situ Implant. Chapter 3: Comparative Pharmacokinetic Study of Different Injectable Donepezil Formulae.