Drug release from Pluronic F-127 gels

Low toxicity, reverse thermal gelation and high drug loading capabilities, suggest that PF-127 gels have great potential as a drug delivery system. The release of benzoic acid and related compounds from Pluronic F-127 (PF-127) gels has been studied in an in vitro release model. Release of the model drugs has been shown to decrease with increasing poloxamer concentration which is probably due to an increase in size and number of micelles and a subsequent decrease in size and number of aqueous channels. The diffusion coefficients of benzoic acid and p-hydroxybenzoic acid have been shown to decrease in an apparent exponential manner with respect to PF-127 concentration. The influence of drug lipophilicity on drug release has been studied by use of a series of p-hydroxybenzoate esters at three different temperatures. An increase in lipophilicity causes a decrease in release rate of the esters due to a greater partitioning into the micellar region within the gel structure. The energies of activation for diffusion of the p-hydroxybenzoate esters were estimated from their temperature dependence and were shown to increase with an increase in lipophilicity.