**5. Conclusion**

Drug carriers are revolutionary delivery systems in the field of medicine. While there have been several studies that reported different types of polymers that has been used to synthesize the carriers, hydrogel-based systems seem to be very promising due to their affordability, production simplicity, and their unique ability to load different types of drugs. Although several gel-based systems have been investigated, designed and IP-protected, it seems only limited number of these product has actually reached the market, which indicates the need for further investigations on improving the performance of current products and develop new ones. This chapter addressed different hydrogel-based drug delivery systems from different perspectives including mechanisms (loading, releasing, and targeting), design (shape and route of administration), and the classes of delivery drugs. These elements are essential when designing and investigating state-of-the-art hydrogel-based delivery systems.
