Development and validation of RP-HPLC method to determine letrozole in different pharmaceutical formulations and its application to studies of drug release from nanoparticles.

This study describes development and subsequent validation of a reversed phase high performance liquid chromatographic (RP-HPLC) method for estimation of letrozole, a new aromatase inhibitor, in raw material, pharmaceutical formulations like tablets and nanoparticles and in release medium. The chromatographic system consisted of a FinePak C, column, an isocratic mobile phase composed of deionized water, acetonitrile and methanol (50:30:20 v/v/v) and UV detection at 240 nm. Letrozole was eluted at 9.8 min with no interfering peak of excipients used for the preparation of dosage forms. The method was linear over the range from 1 to 50 microg/mL in raw drug (R2 = 0.9999). The intra-day and inter-day precision values were in the range of 0.122-0.277%. Limit of detection and limit of quantitation were 0.207 microg/mL and 0.627 microg/mL, respectively. Results were validated statistically according to ICH guidelines in both tablets and nanoparticles. Validation of the method yielded good results concerning range, linearity, precision and accuracy. The method was successfully applied in drug release studies from nanoparticles. The release kinetics was found to be fitted into the Higuchi model.