Effect of Gastrointestinal Protein Adsorption on the In Vitro Release of AZT from Ethylcellulose Microspheres

ABSTRACTThe purpose of this study was to assess the effect of gastrointestinal proteins on the in vitro release of zidovudine (AZT) from ethylcellulose microspheres, and to investigate protein adsorption as a possible mechanism that mediates this effect. AZT release from ethylcellulose microspheres was tested in the presence of different gastrointestinal proteins, both dietary (casein and albumin) and endogenous (pepsin, pancreatin, and mucin) in simulated gastric Jluid and/or simulated intestinal Jluid. The resulting release projiles were compared with those produced in the corresponding release media without the presence of proteins. Protein adsorption on AZT-loaded ethylcellulose microspheres was studied for the five proteins under investigation. The amounts of adsorbed proteins were determined by Jluorescent spectrometry after the protein solution was reacted with fluoraldehyde reagent. All of the investigated proteins were found to slow the release of AZT from ethylcellulose microspheres. At gastric ...