LC and LC-MS study on establishment of degradation pathway of glipizide under forced decomposition conditions

Forced degradation studies on glipizide are conducted under the conditions of hydrolysis, oxidation, photolysis, and dry heat. The solutions are subjected to liquid chromatographic (LC) investigations to establish the number of products formed in each condition. The degradation products are characterized through isolation and subsequent NMR, IR, and MS spectral analyses, or through LC-mass spectrometry (MS) fragmentation pattern study. The drug is shown to degrade in 0.1M HCl at 85 degrees C to two products: 5-methyl-N-[2-(4-sulphamoylphenyl)ethyl]pyrazine-2-carboxamide (II) and methyl N-[4-[2-{(5-methyl-2-pyrazinoyl)amino}ethyl] phenyl]sulfonyl carbamate (III). The latter, a methyl ester, is formed only in the presence of methanol (used as a solubilizer), and does not appear on use of acetonitrile. III is shown to convert to II on continued heating in acid. The drug degrades slowly in water at the same temperature, and both II and III could be seen in the chromatograms until the end of the study. The heating of the drug in alkali (0.1M NaOH) at 85 degrees C yields 5-methyl-2-pyrazinecarboxylic acid (IV), along with a small quantity of 4-(2-aminoethyl) benzenesulfonamide (I). On extended heating in the same condition, a new product, 4-(2-aminoethyl)-N,N-bis[(cyclohexylamino)carbonyl] benzenesulfonamide (VI) is formed in small quantities. At the lower temperature of 40 degrees C, the drug converts under each hydrolytic condition and in both the absence and presence of light to products II, III, or IV, along with a new product, 1-cyclohexyl-3-[[4-(2aminoethyl)phenyl] sulfonyl]urea (V). The light catalyzes formation of V, and it is formed until one or two weeks, after which its level decreases. The drug remains stable in 30% H2O2, except that products II and III appear as small peaks due to acidic character of the peroxide solution. Also, the drug remains unaffected in solid state under thermal and photolytic stress conditions. Based on the results, a more complete picture on degradation pathway of the drug is obtained, highlighting a clear advantage of the approach suggested by International Conference on Harmonization.