Biological and pharmaceutical applications

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Chapter: Pharmaceutical Drugs and Dosage: Interfacial phenomena

Interfacial phenomena are important in the following biological and pharmaceutical applications:

Biological and pharmaceutical applications

Interfacial phenomena are important in the following biological and pharmaceutical applications:

·           Physical stability of biphasic dosage forms, such as suspensions and emulsions, are affected by the stabilization of the solid–liquid and the liquid–liquid interfaces, respectively.

·           Gas exchange in the lung: Biological surfactants in the lung lower the surface tension of the alveolar membrane. Thus, alveoli can expand easily with inspiration and do not collapse at the end of expiration. If there is little or no surfactant in the lungs to assist these processes, the alveoli collapse, leading to respiratory distress syndrome.

·           Preventing absorption after oral overdose and poisoning: Activated charcoal, magnesium oxide, and tannic acid are administered to reduce the absorption of an oral overdose of many drugs such as colchicines, phenytoin, aspirin, and chlorphenamine.

·           Hemoperfusion: Many cases of severe drug overdoses can be treated by direct perfusion of the blood over charcoal granules. Although activated charcoal granules are very effective in adsorbing many toxic materials, they are not safe to use because they tend to embolize par-ticles and remove blood platelets. Charcoal-induced embolism was reduced by microencapsulation of activated charcoal granules in bio-compatible membranes, such as acrylic hydrogels.

·           Adsorption in drug formulation: Some drugs tend to adsorb onto solid surfaces, which may reduce the rate and/or extent of drug release from the dosage form. This is exemplified by ionic interactions of ion-izable drugs with ion-exchange resins. This phenomenon is used to create sustained- or extended-release dosage forms and in the use of resins for oral overdose.

·           Adsorption to packaging components: Adsorption of medicaments onto the container and closure material can reduce the potency of the drug product.

·           Improving drug dissolution: The dissolution rate of poorly soluble drugs can be improved by adsorption of a small amount of surfactant on the surface of drug particles.

·           Protein adsorption: Adsorption of proteins onto surfaces is a fast process and depends on concentration, charge, temperature, and hydrophobicity. Adsorption of protein on hydrophobic surfaces can catalyze its unfolding and aggregation, leading to physical instability in drug product formulation. Thus, containers and closures for the storage and administration of protein therapeutics, including intrave-nous infusion sets, need to be carefully evaluated for protein—surface interaction.

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