Benztropine identification and quantitation in a suicidal overdose

For a human fatality involving suspected overdose with the anticholinergic agent benztropine, GC-MS analysis was utilized for identification, quantitation, and investigation of metabolism. Organic extracts of blood and urine were analyzed by a capillary-column gas chromatograph interfaced with an ion-trap mass spectrometer, which was programmed for wide-spectrum data acquisition. Electron impact and chemical ionization were used for benztropine detection. The chemical structures of the ion fragments are proposed. Benztropine-d3 was synthesized and used as an internal standard. Quantitative determinations of benztropine revealed 0.183 mg/L in blood and 7.12 mg/L in urine from the decedent. Drug concentrations were interpreted relative to the case findings, published data, and a limited evaluation of the therapeutic concentrations in psychiatric patients. In addition, the possible metabolic conversion to norbenztropine was investigated by the synthesis of the norbenztropine derivative. Chromatographic evaluation of samples from the case study did not reveal significant bioconversion via the N-desmethylation pathway.