Isolation and Characterization of Cetirizine Degradation Product: Mechanism of Cetirizine Oxidation

Abstract

The goal of the study was to isolate and analyze a cetirizine degradation product, formed within a PEG-containing formulation and to elucidate the mechanism of oxidation of cetirizine. Cetirizine, formulated in PEG-containing matrix, was subjected to forced degradation conditions in the pH range from 3 to 10, and the product was analyzed by HPLC and LC-MS/MS. Additionally, pure cetirizine was subjected to selective oxidization by hydrogen peroxide and sodium percarbonate. The reaction mixture was purified, and the isolated material was analyzed by (1)H NMR. Oxidation process was investigated in order to model the degradation of cetirizine in PEG-containing formulation. Site of oxidation is proposed based on correlation of the results of forced degradation with ionization scheme of cetirizine. The finding was verified by spiking of cetirizine degradation sample with cetirizine N-oxide reference standard. Degradation of cetirizine in polyethylene glycol arose from the reaction between the drug and the reactive peroxide intermediates such as peroxyl radicals formed through oxidation of PEG. Selective oxidation of cetirizine and isolation/characterization of the oxidation product allowed the identification of the oxidation product as cetirizine N-oxide. The mechanism of oxidation is proposed.