Surface crosslinking for delayed release of proxyphylline from PHEMA hydrogels.

Abstract	Delayed release systems find applications in chronotherapeutics and colon-specific delivery. They have also been considered suitable carriers for the oral delivery of peptides and proteins. In prior work, our research group has reported surface crosslinking as an effective technique to modify drug release profiles for poly(vinyl alcohol) (PVA) hydrogels, reducing the early burst effect in particular. Here, we demonstrate the feasibility of delayed release of proxyphylline from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels via surface crosslinking. Studies on in vitro drug release and the morphology changes of PHEMA hydrogels during swelling and drug release showed that the highly surface crosslinked layers and the ruptures occurring in these layers during swelling were likely responsible for the delayed release. In addition, the initial burst was significantly reduced or even eliminated from the drug release profile for PHEMA to achieve near zero-order release by judicious selection of two surface crosslinking parameters: crosslinking reagent concentration and exposure time used for the surface crosslinking treatment.
Authors	Linfeng Wu, Christopher S Brazel
Journal	International journal of pharmaceutics (Int J Pharm) Vol. 349 Issue 1-2 Pg. 1-10 (Feb 12 2008) ISSN: 0378-5173 [Print] Netherlands
PMID	17825507 (Publication Type: Journal Article)
Chemical References	Bronchodilator Agents Cross-Linking Reagents Delayed-Action Preparations Hydrogels Solutions Water proxyphylline Polyhydroxyethyl Methacrylate Aminophylline Theophylline
Topics	Aminophylline (administration & dosage, analogs & derivatives, chemistry) Bronchodilator Agents (administration & dosage, chemistry) Chemistry, Pharmaceutical Cross-Linking Reagents Delayed-Action Preparations Hydrogels Molecular Weight Polyhydroxyethyl Methacrylate Solutions Surface Properties Theophylline (analogs & derivatives) Water (chemistry)

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