Interaction of Amine Drugs with a Polycarboxylic Acid Ion-Exchange Resin

The interaction of polacrilin potassium, the salt of a polycarboxylic acid ion-exchange resin, with 11 amine drugs was studied. All drugs showed maximum interaction at pH 4.5-5.5. Tertiary amines exhibited a much greater affinity for the resin than primary, secondary, and quaternary amines. Selectivity coefficients were used to express the degree of interaction, with experiments showing that these values remain constant over wide variations in resin, drug, and alkali metal concentrations. Rate studies demonstrated that both adsorption of drug onto the resin and elution from the resin are very rapid. The rapid elution rates, along with decreasing resin affinity for amine drugs above pH 6.0, indicate that the presence of polacrilin potassium in a dosage form should not affect total drug availability in the gastrointestinal tract.