Gentamicin release from hydroxyapatite/poly(ethyl methacrylate)/poly(methyl methacrylate)composites.

In this work the release kinetics of gentamicin sulfate (GEN) in samples composed by hydroxyapatite, poly(methyl methacrylate), and poly(ethyl methacrylate) has been studied. The release study was performed by soaking three samples in simulated body fluid at 37 degrees C; the medium was periodically replaced during 70 days. The concentration of GEN was determined by the o-phtaldialdehyde method. The release profile shows three stages: the first stage, occurring during the first 10 h, corresponds to a fast release (nearly 30% of the drug is released in this period). The second stage is slower and includes from the first 10 h to 16 days, releasing 60% of the total amount of GEN. The final stage is the slowest and it takes from 16 to 70 days (10% of GEN is released). The fraction of released GEN versus square root of time can be fitted to a third order polynomial, corresponding with the model proposed by Cobby et al. (J Pharm Sci 1974;63:725-732). The characterization of the samples after the release study shows that a carbonate hydroxyapatite layer has grown on the whole surface of the composites. Copyright 2000 John Wiley & Sons, Inc.