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IntroductionCyclodextrins (CDs) are a series of natural cyclic oligosaccharides produced by the enzymatic degradation of starch. The most common types include α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, along with their chemically modified derivatives such as HP-β-CD and RM-β-CD. Structurally, cyclodextrins feature a unique truncated cone shape with a **hydrophobic internal cavity** and a **hydrophilic external surface**. This special molecular structure enables them to form stable host-guest inclusion complexes with hydrophobic drug molecules through non-covalent interactions like van der Waals forces and hydrogen bonds. Thanks to this characteristic, cyclodextrins have become indispensable multifunctional raw materials in the modern pharmaceutical industry, widely applied in drug formulation optimization, delivery system construction and clinical disease treatment.Basic Functional Mechanisms in PharmaceuticalsThe core value of cyclodextrins in medicine lies in their inclusion complexation capacity. Firstly, they can significantly **improve the water solubility** of poorly soluble drugs. Many clinical drugs suffer from low aqueous solubility, leading to slow dissolution and low oral bioavailability. After being encapsulated into the cyclodextrin cavity, hydrophobic drug molecules are dispersed in the aqueous environment, greatly accelerating the dissolution rate. Secondly, cyclodextrins act as a molecular protective barrier to **enhance drug stability**, protecting active pharmaceutical ingredients from degradation caused by light, heat, oxidation and pH changes, effectively extending the shelf life of preparations. In addition, they can mask the bitter taste and irritating odor of drugs, reduce gastrointestinal irritation, and realize controlled and targeted drug release to lower toxic and side effects.Core Pharmaceutical Applications1. Improvement of Oral Drug Formulations Oral administration is the most mainstream medication route, and cyclodextrins are extensively used in oral tablets, capsules and oral liquids. For insoluble antifungal drugs such as itraconazole, complexation with HP-β-CD can increase its solubility by nearly 30 times and significantly elevate in vivo absorption efficiency. For traditional Chinese medicine active ingredients and natural bioactive compounds with poor stability, cyclodextrin encapsulation can avoid ingredient loss during processing and storage, while optimizing taste to improve patient medication compliance. Moreover, cyclodextrins can convert liquid oily drugs into solid powder, facilitating the preparation and storage of solid oral preparations. 2. Parenteral and Injectable Preparations Modified cyclodextrins with high safety and low hemolytic activity are ideal excipients for injections, infusions and lyophilized powders. They can stabilize protein and peptide drugs such as insulin, preventing molecular aggregation, denaturation and enzymatic degradation. For lipophilic injections that are difficult to dissolve in water, cyclodextrins replace organic solvents, reducing the irritation and allergic risks caused by solvent residues and improving the safety of intravenous and intramuscular administration. At present, multiple cyclodextrin-containing injectable preparations have been officially launched and applied in clinical anti-infection and anti-tumor treatment. 3. Topical and Ocular Drug Delivery In dermatological ointments, creams and transdermal patches, cyclodextrins can promote the transdermal penetration of active ingredients, maintain stable drug concentration on the skin surface, and prolong the drug action time while reducing skin irritation. In ophthalmic preparations such as eye drops, cyclodextrins improve the solubility of eye drugs, prolong the residence time of drugs on the ocular surface, avoid frequent administration, and protect active ingredients from being diluted by tears, significantly enhancing the therapeutic effect on eye inflammation and corneal diseases. 4. Targeted Drug Delivery and Novel Therapeutic Systems With the development of pharmaceutical nanotechnology, cyclodextrins have evolved from common excipients into core carriers for intelligent drug delivery. They can be combined with polymers, nanosponges and microcapsules to construct slow-release, sustained-release and stimulus-responsive delivery systems, achieving targeted drug accumulation in lesion tissues such as tumors and inflammatory sites. In the research of neurodegenerative diseases like Alzheimer’s and Parkinson’s, cyclodextrin-based delivery systems help drug molecules cross the blood-brain barrier and improve the bioavailability of neuroprotective drugs. In addition, cyclodextrins can also serve as active therapeutic agents, scavenging toxic substances in the body and regulating cholesterol metabolism, showing great potential in the treatment of atherosclerosis and metabolic diseases. 5. Stabilization of Biopharmaceuticals and Gene Delivery Biological drugs including proteins, peptides, nucleic acids and vaccines are prone to activity loss due to environmental changes. Cyclodextrins can form complexes with biomacromolecules to maintain their spatial conformation and biological activity during production, transportation and storage. Meanwhile, cyclodextrin-modified vectors can effectively load gene drugs, protect nucleic acid molecules from enzymatic degradation, and assist targeted gene transfection, providing a new technical path for gene therapy research.Safety and Industrial Application ProspectsNatural and modified cyclodextrins feature low toxicity, good biocompatibility and excellent metabolic safety, and have been approved as pharmaceutical excipients by major pharmacopoeias worldwide. With the continuous progress of modification technology, new cyclodextrin derivatives with higher solubility, lower toxicity and stronger inclusion capacity are constantly emerging. Driven by the demands of innovative drugs, generic drug consistency evaluation and traditional Chinese medicine modernization, cyclodextrins will further expand their application scope in precision drug delivery, personalized preparations and new drug research and development.ConclusionAs a natural green pharmaceutical material, cyclodextrins rely on their unique cavity structure and host-guest inclusion properties to solve key bottlenecks such as poor solubility, low stability and low bioavailability of many drugs. They cover almost all mainstream dosage forms including oral, injectable, topical and ocular preparations, and have expanded from traditional excipients to intelligent delivery carriers and active therapeutic substances. In the future, with the deep integration of nanomedicine and precision therapy, cyclodextrins will play an increasingly important role in promoting pharmaceutical innovation and optimizing clinical medication.