In vitro studies on the transdermal formulation containing pentoxifylline microspheres with poly-L-lactide

In this study, microspheres of Pentoxifylline (PTX) obtained with poly-L-lactide were investigated for drug-polymer ratios of 1:1, 1:5 and 1:10 and the HPLC results of PTX in the microspheres indicated that 1:5 drug-polymer ratio had the highest loading efficiency. For HPLC analysis acetonitrile-water (40:60) was selected as the mobile phase because it yielded the most favorable k' values. Retention times are 4.51 and 7.88 min. for PTX and internal standard (phanecetin), respectively. Calibration curves were linear (r2 > 0.999) in the range of 0.5-10 mg/ml with no significant difference from the origin. Then, matrix controlled transdermal systems containing plain drug or microspheres of drug were prepared. Carrageenan was chosen as a matrix polymer. In vitro release data of the formulations were evaluated kinetically. The results obtained indicate that PTX containing microspheres can be incorporated in carrageenan matrices to form a transdermal therapeutic system.