To identify an alternative swelling medium with a hydrophilic polymer, we have observed that a swelling medium containing only 6% PEG 2000 and 0.9% NaCl failed to protect a hydrophilic coating during electron beam sterilization and subsequent storage at ambient and higher temperatures in an accelerated storage stability test. An unacceptably low dry-out time, below the specified 5 minutes, was obtained. However, when the biological buffer sodium citrate was added to a swelling medium containing PEG 2000, the performance of the stored catheters was as good as or better than the performance of catheters stored with the conventional swelling medium.
