Increasing solubility and bioavailability of drugs
Forming inclusion complexes with poorly soluble drugs can enhance their solubility in water, leading to improved bioavailability and efficacy, as well as allowing for the development of injectable formulations, thereby reducing the required dosage. Factors such as the ratio and type of cyclodextrin compounds, inclusion conditions, preparation methods of complexes, and the form of drugs can all influence the solubility of the inclusion complexes. After being encapsulated by β-cyclodextrin (β-CD), poorly soluble drugs exhibit increased solubility and dissolution rate in water, thereby improving their bioavailability and efficacy by facilitating their passage through biological membranes and the blood-brain barrier. For instance, the solubility of quercetin increased 12 times and the cumulative dissolution rate increased 6 times after encapsulation with β-CD, significantly enhancing the bioavailability of quercetin tablets. Rutin, due to its poor water solubility and low oral absorption, was significantly improved in terms of solubility and bioavailability by forming rutin-β-CD complexes.
Enhancing drug stability
Drugs prone to oxidation, hydrolysis, or volatility can be protected by encapsulating unstable portions within the cavities of cyclodextrins, thereby preventing contact with surrounding molecules and effectively preventing oxidation, hydrolysis, and volatilization, thus increasing stability. For example, dihydroquercetin, highly volatile at 40°C with a residual rate of only 27% after 10 days, maintained a residual rate of over 95% when complexed with β-cyclodextrin under the same conditions. Ursofalk tablets containing various volatile oil components such as fennel and tangerine peel often exhibited oil spots on the surface and deteriorated into dark tablets due to their volatility, leading to unstable quality. However, a new process of encapsulating volatile oils with β-CD overcame this issue, significantly improving the quality of the tablets. Additionally, the formation of CD complexes avoids compatibility issues in combination therapy.
Serving as carriers for sustained and targeted drug delivery
Cyclodextrins can act as carriers for drug storage, controlled release, and increased loading of lipophilic drugs in microspheres, enabling targeted or controlled drug delivery. They can also be utilized in the development of non-pH-dependent osmotic pump tablets. For instance, hydroxypropyl-β-cyclodextrin (HP-β-CD) was employed as a carrier material for magnetically targeted anticancer drug doxorubicin, demonstrating the potential for magnetic targeting drug delivery by studying their interaction and complex formation properties.
Reducing drug toxicity and irritation
The application of cyclodextrin complexes can mask the unpleasant odor and reduce the gastrointestinal irritation of drugs containing irritant components, effectively overcoming their toxicity. For example, podophyllum resin, highly toxic and irritating, was traditionally processed into podophyllum ointment after removing most of the oil. However, the ointment still exhibited high toxicity and irritation. Encapsulation with β-CD reduced its irritation, and clinical verification showed improved ease of use and satisfactory efficacy. Lei Gong Teng, a toxic plant with significant anti-inflammatory and immunosuppressive effects, was utilized for its therapeutic properties while minimizing toxicity through encapsulation with β-CD.
Powdering of volatile oils in traditional Chinese medicine for easier formulation
Encapsulation of volatile oils from traditional Chinese medicine not only prevents their evaporation, thus preserving efficacy, but also facilitates their conversion into powdered solids, making them suitable for various dosage forms. For instance, the inclusion of volatile oils in the formulation of Brain-Ease tablets improved flow properties and prevented discoloration of sugar-coated tablets during storage.
