Drug delivery in the context of Pharma research is mainly concerned with defining a suitable formulation to deliver the drug into the body. In this respect, the drug delivery or more commonly named the drug delivery system (DDS) is defined as a formulation that enables the introduction of a medicinal substance into the body along to improving the safety and efficacy of the medicine. This is accomplished by controlling specific parameters such as the rate, the time, and the place of release of the drug.
Drug delivery methods predominantly rely upon the inherent nature of the intended medicinal/therapeutic use of the product. Thus, the DDS might involve other substances in the formulation to enhance the drug availability in the intended body location. In most cases, such additional substances, or excipients, accounts to the bioavailability of a therapeutic agent as one of the main purposes of formulation development.
Prominent examples of DDS are formulations, which use these excipients to target specific cells or parts in the body. This can be cumbersome as the body has several barrier functions built in and therefore, hinders the targeted release of the drug. Such barriers in the body are known and studied, such as the blood-brain barrier or the blood-eye barrier. To overcome these barriers, smart formulations are needed. Excipients in such cases can for example be other molecules, nano- or microscale structures, such as nano beads, micelles, vesicles or functionalized polymers, to name a few.