Abstract

SERRANO-MEDINA, Aracely  and  CORNEJO-BRAVO, José Manuel. Buffer Effects on Drug Release Kinetics From Acidic Hydrophobic Gel Discs. J. Mex. Chem. Soc [online]. 2011, vol.55, n.1, pp.02-06. ISSN 1870-249X.

Here we study the variability of drug release rates from hydrophobic polyacid gels, due to the presence of basic buffer species. Release kinetics of the model drug salicylic acid from crosslinked poly(methyl methacrylate-co-methacrylic acid) hydrogels were measured as a function of buffer concentration, buffer acidity (pKa), and solution pH, with total ionic strength (I) held constant. Results show that the release rate of salicylic acid is determined by the concentration of buffering species in the nonionized, conjugated basic form, and not by the pH itself. Since it is difficult to control the concentration and composition of weak electrolytes in the gastrointestinal tract, precise pH-modulated controlled release from hydrophobic polyacid gels may be difficult to achieve. These gels may be more suitable in cases where pH-triggered release is desired, but precise rate control is not warranted.

Keywords : hydrogel; polyelectrolyte gel; swelling-controlled release; buffer effect; methacrylates.

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