Abstract. Colon-specific drug delivery systems (CDDS) are desirable for the treatment of a range of local diseases such as ulcerative colitis, Crohn's disease, irritable bowel syndrome, chronic pancreatitis, and colonic cancer. In addition, the colon can be a potential site for the systemic absorption of several drugs to treat non-colonic conditions. Drugs such as proteins and peptides that are known to degrade in the extreme gastric pH, if delivered to the colon intact, can be systemically absorbed by colonic mucosa. In order to achieve effective therapeutic outcomes, it is imperative that the designed delivery system specifically targets the drugs into the colon. Several formulation approaches have been explored in the development colon-targeted drug delivery systems. These approaches involve the use of formulation components that interact with one or more aspects of gastrointestinal (GI) physiology, such as the difference in the pH along the GI tract, the presence of colonic microflora, and enzymes, to achieve colon targeting. This article highlights the factors influencing colon-specific drug delivery and colonic bioavailability, and the limitations associated with CDDS. Further, the review provides a systematic discussion of various conventional, as well as relatively newer formulation approaches/technologies currently being utilized for the development of CDDS.

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The physicochemical and biological properties of active pharmaceutical ingredients (APIs) are greatly affected by their salt forms. The choice of a particular salt formulation is based on numerous factors such as API chemistry, intended dosage form, pharmacokinetics, and pharmacodynamics. The appropriate salt can improve the overall therapeutic and pharmaceutical effects of an API. However, the incorrect salt form can have the opposite effect, and can be quite detrimental for overall drug development. This review summarizes several criteria for choosing the appropriate salt forms, along with the effects of salt forms on the pharmaceutical properties of APIs. In addition to a comprehensive review of the selection criteria, this review also gives a brief historic perspective of the salt selection processes.

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