The therapeutic action of medications occurs when they bind to specific receptors in the tissues that they are intended to treat. The treatment’s efficacy, however, declines if the medication does not reach to the intended location at the desired rate and required concentration. Bioavailability, the rate and extent to which the active substance reaches its site of action in the body, is essential for the success of the treatment. To achieve therapeutic efficacy, the concentration of the drug in the plasma must remain within the therapeutic dose range, i.e., between the “minimum effective concentration” and the “toxic level.” In traditional drug applications, high doses or repeated doses are often administered at certain intervals to achieve the desired therapeutic effect. However, these methods, whether through injection or oral administration, can lead to patient discomfort. Furthermore, high doses can result in side effects or toxicity. The short half-life of certain bioactive substances, like peptides and proteins, in the bloodstream, along with their degradation before reaching the target tissue, further reduces therapeutic effectiveness. To address these drawbacks, controlled drug release systems are developed using membranes, nanoparticles, liposomes, and hydrogels.