The complexation of cyclodextrins: a promising approach in pharmaceutical formulation. A literature review

Abstract

Complexation, a crucial method for enhancing the physicochemical properties of pharmaceutical compounds, involves the reversible association of substrates with ligands to form complexes. Among various complexing agents, cyclodextrins (CDs)—cyclic oligosaccharides composed of glucopyra-nose units—exemplify inclusion complexes, wherein a “guest” molecule is encapsulated within a “host” structure without covalent bonds. This interaction significantly alters the physicochemical parameters of the guest, enhancing traits such as solubility, stability, and bioavailability. Discovered in 1891 and structurally defined in the 1940s, CDs have gained prominence in pharmaceutical formu-lations, as ongoing research expands their application. The complexation technique primarily utilizes association constants and stoichiometry determined through phase solubility analysis. Factors influ-encing complexation, including sterics and charge density, are elaborated, highlighting the compat-ibility of guest molecules with CD cavity dimensions. Furthermore, the discussion on drug stability and absorption dynamics underscores the role of CDs in enhancing the eficacy of poorly soluble drugs. Ultimately, this review examines the implications of CD complexation on drug formulations, addressing challenges in regulatory frameworks across different regions, and underscores the vital role of CDs in modern pharmaceutical development.