Chemical interactions between drugs containing reactive amines with hydrolyzable insoluble biopolymers in aqueous solutions.

Chemical reactions between drugs containing reactive amines with hydrolyzable polymers in buffer solutions were investigated. Phenylalkylamines with increasing nucleophilic reactivity were used as model drugs. Solutions of phenylalkylamines were reacted heterogeneously with representative biodegradable polyanhydride and polyester powders in various pH solutions, and the recovery of the amines from the solutions was determined. Poly(sebacic acid), a reactive polyanhydride, reacted by amide formation with the tested amines and their respective HCl salts when exposed to physiologic pH (pH 7.4). However, at pH 5.0 no interaction occurred. The aromatic polyanhydride, PCPP, and the polyesters based on lactic acid and caprolactone did react with the amine derivatives at pH 7.4, but at a slower rate. The reaction can be avoided with appropriate salt derivatives of the amines.