Additive model for the evaluation of interactions between aqueous solutes and multi-component container materials.

The interaction between aqueous model solutes and various current or potential parenteral solution container materials was studied. Materials examined included composite polymers (plasticized PVC and co-extruded composites) and their individual components. For each material studied (component and composite), the equilibrium interaction constant (Eb), which describes the distribution of a solute between a container and its contained solution, can be related to the solute's octanol-water (Po-w) and hexane-water (Ph-w) partition coefficients via a bimodal Collander-type expression: log Eb = a log Po-w + b log Ph-w + c Additionally, the interaction of the composites was found to be equivalent to the weighted average of the interaction properties of its individual components. That is, Eb,composite = sigma Wi x Eb,i where i represents an individual component of the composite and Wi represents the weight fraction of that component in the composite. The impact of the interaction properties of the components on the behavior of the composites is discussed; thus, for example, the interaction properties exhibited by plasticized PVC is dominated by the behavior of the plasticizer since unplasticized PVC itself exhibits only minimal interaction with aqueous solutes.