Substantial drop of plasticizer migration from polyvinyl chloride catheters using co-extruded thermoplastic polyurethane layers

The flexibility and required softness of polyvinyl chloride (PVC) -one of the most widely used polymeric materials for medical device production- is achieved by the addition of an appropriate amount of plasticizer (up to 40 %) into the polymer matrix. As plasticizers are not chemically bound to PVC they can easily migrate to surrounding media such as saliva, blood, plasma or serum resulting in undesirable toxic effects. Migrations of plasticizers from PVC can be significantly suppressed by embedding plasticized PVC into another -'less harmful'polymer, thus preventing its direct contact with the surrounding media. Co-extruded TPU/PVC/TPU catheters were prepared with various thicknesses of thermoplastic polyurethane (TPU) layers to evaluate the retarding effect of the protective TPU layer on releasing bis(2-ethylhexyl) terephthalate plasticizer (the only one approved by European Pharmacopoeia). A substantial difference was found in the migration of plasticizer from non-coated and coated (three-layer) catheters into a saline solution and acetonitrile which was dependent on the time exposed to the concentration of released plasticizer determined simultaneously by reverse-phase liquid chromatographic technique and weight loss analysis. The results proved that the TPU inner and outer layers represent an efficient protective barrier and significantly reduce amounts of released plasticizer.