drug analysis drug identification 30 nonhuman 28 theoretical study 24 mass spectrometry 22 radioisotope 22 in vitro study 20 drug synthesis 18 priority journal 16 Animal 14 Support, Non-U.S. Gov't 14 animal experiment 14 preliminary communication 14 Rats 12 drug determination 12 drug isolation 12 nuclear magnetic resonance 12 Male 10 drug comparison 10 drug mechanism 10 drug structure 10 infrared spectrometry 10 methodology 10 rat 10 thin layer chromatography 10 blood and hemopoietic system 8 drug blood level 8 drug metabolism 8 human 8 human cell 8