Simultaneous identification and validated quantification of 11 oral hypoglycaemic drugs in plasma by electrospray ionisation liquid chromatography-mass spectrometry

The detection of diabetic metabolism disorders raises problems in forensic practice and sudden death with a subsequent negative autopsy finding is a common problem. In the case of an unclear hypoglycaemia, the detection of oral antidiabetics allows the differentiation of hypoglycaemia due to oral antidiabetics from that due to other reasons (insulin-induced, insulinoma). The development of an electrospray ionisation (ESI) liquid chromatography-tandem mass spectrometry (LC-MS/MS) procedure for the simultaneous identification and quantification of oral antidiabetics of the sulfonylurea, the glinide, the thiazolidinedione and the gliptin types in human plasma is desired. The following analytes were included: glimepiride, glibenclamide, gliquidone, glibornuride, glisoxepide, glipizide and gliclazide (sulfonylurea type), nateglinide and repaglinide (glinide type), rosiglitazone and pioglitazone (thiazolidinedione type) and the dipeptidyl peptidase inhibitors vildagliptin, sitagliptin and saxagliptin. After a liquid-liquid extraction with tert-butyl methyl ether at two pHs, the oral antidiabetics were separated with fast gradient elution over a C-8 column. Identification of the oral antidiabetics was achieved by two specific ion transitions of each analyte in multiple reaction monitoring mode. Quantification was performed by referring the most intense ion transition peak areas to peak areas of the ion transitions of deuterated oral antidiabetics (hydroxytolbutamide-d (9) for the sulfonylureas, repaglinide-ethyl-d (5) for the glinides, pioglitazone-d (4) for the thiazolidinediones and vildagliptin-d (3) for the gliptins). The assay was validated according to international guidelines. The LC-MS/MS assay allows the simultaneous identification of 14 oral antidiabetics and quantification of 11 oral antidiabetics in plasma in the ESI mode in a single run. Linearity is shown up to overdose concentrations. The limits of detection with a signal-noise-ratio greater than 3 were below 1 ng/ml for all analytes. Recoveries ranged from 78 to 105%; for vildagliptin and saxagliptin recoveries were worse (45%) owing to their hydrophilic character. Intraday and interday precision and accuracy were below 20% for 11 drugs at three concentrations. For the gliptins, several validation parameters were out of range and, therefore, quantitatively this method is inappropriate.