Isolation and characterization of cetirizine degradation product: mechanism of cetirizine oxidation.

Purpose: 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.

Methods: 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.

Farnesol as an inhibitor and substrate for rabbit liver microsomal P450 enzymes.

Farnesol and the related isoprenoids, geranylgeraniol, geranylgeranyl pyrophosphate, and farnesyl pyrophosphate, are produced in the endoplasmic reticulum of hepatocytes in mammals, and each serve important biological functions. Of these compounds, only farnesol was shown to significantly inhibit rabbit liver microsomal cytochrome P450 enzymes. The observed inhibition appeared to be reversible, and was not strictly competitive, but rather mixed in nature.