LC-MS/MS method for the detection of common laxatives.

Laxatives refer to a group of diverse substances used to induce bowel movements. There exist various classes of laxatives, which work through different pharmacological means. Based on the potential medical cause of use, one particular class of laxative may be preferred over another. Additionally, abuse of laxatives in both adults and children occurs. Some of the signs and symptoms of excessive laxative use/abuse can not only mimic various pathological conditions, but cause such conditions. Based on the potential abuse of laxatives, as well as for compliance purposes, a test to identify the use of common laxatives is of significant value. While stool and stool water can be used for such analyses, isolation and identification of analytes can be difficult due to matrix constituents and potential interferences. Ideally, a sensitive urine test for detection of laxative use/abuse with specific detection would be preferable. Described is an LC-MS/MS procedure for the detection of four metabolites related to common laxatives-desacetylbisacodyl, aloe-emodin, emodin, and rhein. Deuterated internal standards for desacetylbisacodyl and emodin are employed while an analog internal standard, biochanin A is used for rhein and aloe-emodin. Sample preparation consists of deconjugation of analytes in urine followed by a simple organic solvent extraction. Analysis is carried out using a pentafluorophenyl column employing a gradient mobile phase of formic acid in water/methanol. Mass spectral ionization conditions employ both positive and negative ESI. Two transitions are monitored for each analyte of interest.