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The load and release characteristics on a strong cationic ion-exchange fiber: kinetics, thermodynamics, and influences.

Yuan J, Gao Y, Wang X, Liu H, Che X, Xu L, Yang Y, Wang Q, Wang Y, Li S - Drug Des Devel Ther (2014)

Bottom Line: The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion.Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences.The drug-fiber complexes exhibited sustained release.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China.

ABSTRACT
Ion-exchange fibers were different from conventional ion-exchange resins in their non-cross-linked structure. The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion. Therefore, this work aimed to investigate the load and release characteristics of five model drugs with the strong cationic ion-exchange fiber ZB-1. Drugs were loaded using a batch process and released in United States Pharmacopoeia (USP) dissolution apparatus 2. Opposing exchange kinetics, suitable for the special structure of the fiber, were developed for describing the exchange process with the help of thermodynamics, which illustrated that the load was controlled by an ionic reaction. The molecular weight was the most important factor to influence the drug load and release rate. Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences. The drug-fiber complexes exhibited sustained release. Different kinds and concentrations of counter ions or different amounts of drug-fiber complexes in the release medium affected the release behavior, while the pH value was independent of it. The groundwork for in-depth exploration and further application of ion-exchange fibers has been laid.

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The release curves of diltiazem-fiber complexes in pH 1.2 solution with different doses (weighed equivalent to 30, 60 and 120 mg diltiazem hydrochloride).
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f9-dddt-8-945: The release curves of diltiazem-fiber complexes in pH 1.2 solution with different doses (weighed equivalent to 30, 60 and 120 mg diltiazem hydrochloride).

Mentions: The release profiles for venlafaxine hydrochloride from the fiber complexes under various external conditions are shown in Figure 8. Different kinds and concentrations of counter ions in the release medium affect the release behavior, while the pH value is independent of it once the concentrations of counter ions in solutions are adjusted by NaCl. The order of the extent of release for the five extraction ions was Ca2+ > Mg2+ > K+ > Na+ > H+. Although each kind of ion has its own special affinity for the ion-exchange fibers, the ability of the divalent ions is about one time greater than that for the monovalent ions, illustrating that the ion exchange is a stoichiometric reaction. When the molar amount of sodium ions was equal, ten-fold, or hundred-fold as compared to the drug ions in the fiber, the release percentages of the drug from the fiber were 17%, 46%, and 81%, respectively. The reason for this is that the increase in the molar amount of counter ions shifts the equilibrium toward drug release. Similarly, the release extent could also become higher as the solution volume increases. Prabhu et al28 reported that the release of diltiazem hydrochloride from resinates is about 40% in pH 1.2 solution in the same apparatus. In comparison, in our work, the release of the drugs from the complexes was more than 80%. The drug dose used was different in the two experiments (30 mg in this work and 120 mg in the previous report). Figure 9 shows the dissolution tests of three doses of diltiazem–fiber complexes. The drug release is irrelevant to the structure; the drug release is determined by the ionic reaction. The release of drug is also not due to the dissolution of drug powder. Once the ionic reaction equilibrium was established between the drugs in fibers and that in release medium, the release was not continued though a good sink condition was maintained in release medium. As the dose decreased, the relative concentration of the extraction solution increased so as to shift the reaction toward drug release and make the release extent higher. Therefore, this dissolution method is more suitable for the release of small doses of drugs from ion-exchange fibers.


The load and release characteristics on a strong cationic ion-exchange fiber: kinetics, thermodynamics, and influences.

Yuan J, Gao Y, Wang X, Liu H, Che X, Xu L, Yang Y, Wang Q, Wang Y, Li S - Drug Des Devel Ther (2014)

The release curves of diltiazem-fiber complexes in pH 1.2 solution with different doses (weighed equivalent to 30, 60 and 120 mg diltiazem hydrochloride).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109635&req=5

f9-dddt-8-945: The release curves of diltiazem-fiber complexes in pH 1.2 solution with different doses (weighed equivalent to 30, 60 and 120 mg diltiazem hydrochloride).
Mentions: The release profiles for venlafaxine hydrochloride from the fiber complexes under various external conditions are shown in Figure 8. Different kinds and concentrations of counter ions in the release medium affect the release behavior, while the pH value is independent of it once the concentrations of counter ions in solutions are adjusted by NaCl. The order of the extent of release for the five extraction ions was Ca2+ > Mg2+ > K+ > Na+ > H+. Although each kind of ion has its own special affinity for the ion-exchange fibers, the ability of the divalent ions is about one time greater than that for the monovalent ions, illustrating that the ion exchange is a stoichiometric reaction. When the molar amount of sodium ions was equal, ten-fold, or hundred-fold as compared to the drug ions in the fiber, the release percentages of the drug from the fiber were 17%, 46%, and 81%, respectively. The reason for this is that the increase in the molar amount of counter ions shifts the equilibrium toward drug release. Similarly, the release extent could also become higher as the solution volume increases. Prabhu et al28 reported that the release of diltiazem hydrochloride from resinates is about 40% in pH 1.2 solution in the same apparatus. In comparison, in our work, the release of the drugs from the complexes was more than 80%. The drug dose used was different in the two experiments (30 mg in this work and 120 mg in the previous report). Figure 9 shows the dissolution tests of three doses of diltiazem–fiber complexes. The drug release is irrelevant to the structure; the drug release is determined by the ionic reaction. The release of drug is also not due to the dissolution of drug powder. Once the ionic reaction equilibrium was established between the drugs in fibers and that in release medium, the release was not continued though a good sink condition was maintained in release medium. As the dose decreased, the relative concentration of the extraction solution increased so as to shift the reaction toward drug release and make the release extent higher. Therefore, this dissolution method is more suitable for the release of small doses of drugs from ion-exchange fibers.

Bottom Line: The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion.Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences.The drug-fiber complexes exhibited sustained release.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China.

ABSTRACT
Ion-exchange fibers were different from conventional ion-exchange resins in their non-cross-linked structure. The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion. Therefore, this work aimed to investigate the load and release characteristics of five model drugs with the strong cationic ion-exchange fiber ZB-1. Drugs were loaded using a batch process and released in United States Pharmacopoeia (USP) dissolution apparatus 2. Opposing exchange kinetics, suitable for the special structure of the fiber, were developed for describing the exchange process with the help of thermodynamics, which illustrated that the load was controlled by an ionic reaction. The molecular weight was the most important factor to influence the drug load and release rate. Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences. The drug-fiber complexes exhibited sustained release. Different kinds and concentrations of counter ions or different amounts of drug-fiber complexes in the release medium affected the release behavior, while the pH value was independent of it. The groundwork for in-depth exploration and further application of ion-exchange fibers has been laid.

Show MeSH