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At least 73 records · Page 4Linked to original sources
PubMed2007

Drug release properties of polymer coated ion-exchange resin complexes: experimental and theoretical evaluation.

Although ion-exchange resins have been used widely as drug delivery systems, their exact release kinetics has not been reported yet. Usually only the rate-limiting step has been taken into account and the rest of the steps have been ignored as instantaneous processes. To investigate the exact release kinetics of polymer-coated drug/ion-exchange resin complexes for sustained drug delivery, the results of new mathematical modeling were compared with experimental results. Drug/resin complexes with a model drug, dextromethorphan, were prepared and used as cores for fluid-bed coating. An aqueous colloidal dispersion of poly(vinyl acetate) was applied for the coating. A comprehensive mathematical model was developed using a mechanistic approach by considering diffusion, swelling, and ion-exchange processes solved by numerical techniques. The rate-limiting factor of the uncoated resin particles was diffusion through the core matrix. Similarly, in the coated particles the rate-limiting factor was diffusion through the coating membrane. The mathematical model has captured the phenomena observed during experimental evaluations and the release dynamics from uncoated and coated (at different coat levels) particles were predicted accurately (maximum RMSE 2.4%). The mathematical model is a useful tool to theoretically evaluate the drug release properties from coated ion-exchange complexes thus can be used for design purposes.

Anion Exchange Resins↗
PubMed1981

Sustained-release drug delivery system I: Coated ion-exchange resin system for phenylpropanolamine and other drugs.

Ion-exchange resin-drug complexes have been used to formulate sustained-release products of acidic and basic drugs. However, sustained release may be difficult to achieve due to many variables. A novel technique is reported that minimizes these variables by providing a polymeric film coating to the ion-exchange resin-drug complex particles, making drug release from these particles diffusion controlled. Direct application of an atomized polymer solution to the fluidized ion-exchange resin-drug complex particles was ineffective in controlling drug release since the coating came off in the dissolution medium due to swelling and fracturing of the particles. Pretreatment of the ion-exchange resin-drug complex particles with an agent such as polyethylene glycol was essential for the particles to retain their geometry and coating during dissolution. With divinylbenzenesulfonic acid resin complexed with phenylpropanolamine as a model, mixtures of ethylcellulose-coated and uncoated resin-drug complex particles were prepared. These mixtures gave varying drug release profiles that showed rank-order correlation with plasma concentration profiles obtained in bioavailability studies with suspension dosage forms.

Biological Availability↗
PubMed2006

Advances in cement solidification technology for waste radioactive ion exchange resins: a review.

Treatment and disposal of waste radioactive ion exchange resins is one of the most urgent problems for nuclear industries in China. Cement solidification technology has many advantages, such as requiring simple equipment, easy scaling-up, low working temperature, no trouble of gas cleaning and low cost. It is a suitable technology for treatment of waste radioactive resins, and has been widely used. The new developments and theoretical basis of cement solidification of radioactive resins were introduced in this paper. The cement solidification technology suitable for China and the questions needed to solve were also discussed.

Hot Temperature↗