Investigation on the photochemical stability of lercanidipine and its determination in tablets by HPLC-UV and LC-ESI-MS/MS.

The photostability of lercanidipine, a dihydropyridine calcium-channel blocker used in the treatment of the hypertension, was studied. Drug substance and its solutions and formulations were exposed to UV-A radiations (solar simulator) and the photodegradation process was monitored by UV spectrophotometry, HPLC and HPLC-mass spectrometry. The effect of the solvent (ethanol and ethanol/PBS 1:1 v/v) on the photodegradation pathway and kinetic was evaluated. Lercanidipine and its photodegradation products were separated by a selective reversed-phase HPLC method and the main photoproducts were characterized by HPLC-MS/MS analysis, using an electrospray ionization source (ESI) and an ion trap analyzer. Photochemical reactions, involved in the photodegradation of lercanidipine, include aromatisation of the dihydropyridine moiety, formation of nitrosoderivatives and N-dealkylation in the side chain. The developed stability-indicating HPLC method was then applied to the quality control of commercially available lercanidipine formulations (tablets).