Uptake of drugs by catheters: the influence of the drug molecule on sorption by polyurethane catheters

The sorption of drugs by indwelling intravenous catheters may have clinical consequences both by alteration of the dose received by the patient and by physically affecting the catheter materials themselves which may lead to changes in mechanical properties and biocompatibility. Studies of drug sorption to new catheter materials are therefore important. PellethaneTM, a polyurethane increasingly used in vascular access catheters, is as yet little studied in terms of its capacity for drug sorption. In this work a range of drugs known to be sorbed by PVC infusion sets were studied with respect to their sorption by Pellethane catheters. Standard lengths of catheter were incubated with solutions of drugs and samples of the solution were taken at intervals, assayed spectrophotometrically and compared with control solutions incubated without catheter. Losses from solution of up to 93% were found after 24 h. A series of highly sorbing and clinically relevant drugs was identified and their uptake was studied until equilibrium had been reached. A correlation was evident between the octanol/water partition coefficient and the fraction of drug taken up from solution at equilibrium, with the more hydrophobic drugs being taken up to a greater extent by the catheter.