Inventory management is one of the essential functions of a company to perform efficiently and effectively. Efficient inventory medicines management in pharmacies require close attention to assure availability of the right drugs in the right quantities, at reasonable prices, and at recognized standards of quality throughout the year without any stock-out periods in between. This paper develops a novel dynamic inventory model through integrating multiple approaches to optimize inventory while minimizing inventory cost and assuring medicines availability. Also, the developed model is able to measures the effectiveness of inventory systems of pharmacies. The case study reviews and analysis a current inventory management method of a local pharmacy in Jeddah, KSA. The findings compared currant applied method and developed model. The developed inventory model helps the pharmacy to reduce cost by 14.38% while satisfying 100% service level rate.