Real-time UV imaging of piroxicam diffusion and distribution from oil solutions into gels mimicking the subcutaneous matrix

A novel real-time UV imaging approach for non-intrusive investigation of the diffusion and partitioning phenomena occurring during piroxicam release from medium chain triglyceride (MCT) solution into two hydrogel matrices is described. Two binary polymer/buffer gel matrices, 0.5% (w/v) agarose and 25% (w/v) Pluronic F127, were applied as simple models mimicking the subcutaneous tissue. The evolution of the absorbance maps as a function of time provided detailed information on the piroxicam release processes upon the exposure of the gel matrices to MCT. Using calibration curves, the concentration maps of piroxicam in the UV imaging area were determined. Regression of the longitudinal concentration–distance profiles, which were obtained using expressions derived from Fick’s second law, provided the diffusivity and the distribution coefficients of piroxicam penetrated into the gels. The obtained MCT–agarose (pH 7.4) distribution coefficient of 1.4 was identical to the MCT–aqueous (pH 7.4) distribution coefficient determined by the shake-flask method whereas that of the MCT–Pluronic F127 system was four times less. The experimental data show that UV imaging may have considerable potential for investigating the transport properties of drug formulations intended for the subcutaneous administration.

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