Time-course measurements of drugs and metabolites transferred from fingertips after drug administration: usefulness of fingerprints for drug testing

We evaluated whether a fingerprint, which consists of secretions from the fingertips, is a suitable biological sample for drug testing. A commercially available cold medicine containing ibuprofen, dihydrocodeine, chlorpheniramine, and methylephedrine was administered to healthy subjects. The subjects washed their hands with tap water and hand soap to remove the external contaminants, and then pressed a fingertip onto wet filter paper at fixed sampling times (from 2 h to 7 days). The analytes on the filter paper were dissolved in 25 % methanol-water, and a large volume (50 mu l) of the extract was analyzed by liquid chromatography-tandem mass spectrometry. The relationship between the sampling times and the concentration of analytes in fingerprints was examined. The results were compared with drug concentrations in blood samples. Most of the drugs and their metabolites were detected from fingerprints at 7 days after drug administration. The fingerprint sample preparation is rapid (ca. 3 min) and simple, and the limits of detection were 0.1 pg/fingerprint for dihydrocodeine, chlorpheniramine, and methylephedrine. We demonstrate that drugs can be detected in fingerprints at later sampling times with more rapid and simpler sample preparation than in blood. The method should be applicable to drug testing in criminal investigations.