Drug delivery systems refer to the delivery of the required amount of drugs to the targeted site or targeted organ of the body to achieve the desired therapeutic effect. It protects the drug from degradation and carries it wherever it needs to go in the body. Drug delivery systems alter the drug's pharmacokinetics and specificity by formulating it with different excipients, drug carriers, and medical devices.
Cyclodextrins (CDs) have been proven as drug carrier candidates in drug delivery systems because of their unique structure and inclusion properties, which can be used in almost all drug delivery systems.
Advantages of CDs in Drug Delivery
CDs are mainly used as complexing agents to change the physical, chemical and biological properties of guest molecules by forming CD inclusion complexes with drug molecules. Here we mainly explain why CDs are becoming increasingly popular in the field of drug delivery by introducing the advantages of CD on the solubility, bioavailability, stability, and irritation of drug molecules [1].
- Improving the solubility of drugs: CD can improve the water solubility of many poorly soluble drugs by forming inclusion complexes with their apolar molecules or functional groups because most of the hydrophobic portion of the drug molecule can be hidden in the internal cavity of the CD.
- Improve the bioavailability of drugs: When the drug is complexed with CD, its solubility increases, which is conducive to drug absorption. Additionally, drug molecules complexed with CD also prevent the crystallization of active ingredients, improving their bioavailability.
- Improve the stability of drugs: The active molecules in the drug are entrapped within the CD cavity after complexation, which improves the chemical, physical and thermal stability of the active molecules.
- Reduce the irritation of drugs to the body: Some drugs that irritate the stomach, skin or eyes can effectively reduce their irritation after forming CD inclusion complexes. In addition, when this CD inclusion complex is dissociated and the drug is released in the body, the local free concentration of the drug is always kept below levels that may irritate the mucosa.
Drug Delivery Systems Based on CDs
Due to its multiple advantages over drug molecules, CD can be used in almost all drug delivery systems, including oral drug delivery, rectal drug delivery systems, nasal drug delivery systems, transdermal drug delivery, ocular drug delivery, controlled and targeted drug delivery systems, peptide and protein delivery, and gene and oligonucleotide delivery. The applications of CDs in three common drug delivery systems are briefly described below [1].
- Oral drug delivery system
The oral route has been the most popular method of drug delivery since ancient times. The complexation of drugs with CDs can increase the dissolution rate of poorly soluble drugs in oral drug delivery systems. Drugs can be delivered through aqueous media to the lipophilic absorption surfaces of the gastrointestinal tract using CDs, especially hydrophilic CDs. Notably, rapid dissolving complexes with CDs have been formulated for buccal and sublingual administration.
- Rectal drug delivery system
Rectal drug delivery system using the rectal mucosa can be effectively applied to deliver drugs to comatose patients, children, and infants. Nevertheless, the rectal drug delivery system only offers a very small area to absorb drugs, resulting in an erratic release of drugs. The non-irritating properties of CD and its ability to inhibit the reverse diffusion of drugs into vehicles make it an attractive excipient for rectal drug delivery system. CDs have been reported in the literature for the delivery of drugs, such as 4-biphenylethyl ester, insulin, and morphine.
- Nasal drug delivery system
Nasal drug delivery system using nasal mucosa is a novel system to deliver high potency drugs. However, it has low oral bioavailability due to extensive gastrointestinal breakdown and high liver first-pass effects. CDs are able to enhance drug penetration across the nasal epithelium in a reversible way. What's more, CDs are also non-irritating and non-allergic, do not interfere with nasal mucociliary function, and do not produce local or systemic effects, making them ideal excipients for nasal drug delivery systems.
Alfa Chemistry is dedicated to the manufacture of CDs. We offer high-quality native CDs, CD derivatives, and CD inclusion complexes. We have strong supply capabilities and can provide products at the kilogram level. Please feel free to contact us and we will serve you wholeheartedly.
Reference
- Tiwari, G.; et al. Cyclodextrins in delivery systems: Applications. J Pharm Bioallied Sci. 2010, 2(2): 72–79.
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