Cyclodextrins (CDs) are cyclic oligosaccharides with hydrophilic outer surfaces and lipophilic inner cavities, capable of forming noncovalent inclusion complexes with various guest molecules. They are widely used in drug delivery to enhance solubility, bioavailability, and stability of drugs, particularly for proteins, peptides, and genes. CDs can be used as excipients in drug formulations and are involved in the design of various delivery systems such as liposomes, microspheres, microcapsules, and nanoparticles. Different CD derivatives, such as α-CD, β-CD, γ-CD, and δ-CD, have varying cavity sizes and solubility properties, affecting their complexation abilities. β-CD is widely used due to its availability and cavity size suitable for a wide range of drugs, but its low aqueous solubility and nephrotoxicity limit its use. Chemically modified CDs, such as HP-β-CD and SBE-β-CD, have enhanced solubility and stability. Factors influencing complexation include CD type, charge, temperature, and preparation method. CDs can improve drug solubility, dissolution, bioavailability, and stability, and reduce toxicity. They are also used in various delivery routes, including oral, parenteral, ocular, nasal, and rectal. CDs can enhance drug permeability by making the drug available at the biological barrier surface. They are also used in controlled drug delivery systems to achieve targeted and sustained release. CDs have a significant impact on drug pharmacokinetics and can be used to improve drug absorption and reduce toxicity. CDs are also used in formulations to enhance drug stability and reduce irritation. The regulatory and patent status of CDs varies, with some CDs being available in bulk quantities and others synthesized in the laboratory. CDs are considered safe and effective for drug delivery, with their use in various formulations being well-documented.Cyclodextrins (CDs) are cyclic oligosaccharides with hydrophilic outer surfaces and lipophilic inner cavities, capable of forming noncovalent inclusion complexes with various guest molecules. They are widely used in drug delivery to enhance solubility, bioavailability, and stability of drugs, particularly for proteins, peptides, and genes. CDs can be used as excipients in drug formulations and are involved in the design of various delivery systems such as liposomes, microspheres, microcapsules, and nanoparticles. Different CD derivatives, such as α-CD, β-CD, γ-CD, and δ-CD, have varying cavity sizes and solubility properties, affecting their complexation abilities. β-CD is widely used due to its availability and cavity size suitable for a wide range of drugs, but its low aqueous solubility and nephrotoxicity limit its use. Chemically modified CDs, such as HP-β-CD and SBE-β-CD, have enhanced solubility and stability. Factors influencing complexation include CD type, charge, temperature, and preparation method. CDs can improve drug solubility, dissolution, bioavailability, and stability, and reduce toxicity. They are also used in various delivery routes, including oral, parenteral, ocular, nasal, and rectal. CDs can enhance drug permeability by making the drug available at the biological barrier surface. They are also used in controlled drug delivery systems to achieve targeted and sustained release. CDs have a significant impact on drug pharmacokinetics and can be used to improve drug absorption and reduce toxicity. CDs are also used in formulations to enhance drug stability and reduce irritation. The regulatory and patent status of CDs varies, with some CDs being available in bulk quantities and others synthesized in the laboratory. CDs are considered safe and effective for drug delivery, with their use in various formulations being well-documented.