Comparative study between active and passive exposure of methamphetamine vapor in mice

Abstract

Heating methamphetamine (METH) crystal to produce vapor has been a method of substance abuse in young people since the mid-1990s. However, there are little data on the relationship between the urinary concentration of METH and exposure to METH vapor in humans. As a result, drug suspects sometimes claim in court that the METH detected in their urine was due to passive exposure. Therefore, this study aimed to clarify the different effects of active and passive METH exposure on urinary METH concentration in an animal model of METH vapor inhalation. Mice were exposed to METH vapor under active exposure (conditions 1), mimicked passive exposure in a car (conditions 2), and mimicked passive exposure in a room (conditions 3). Urine was collected every 24 h after exposure for 96 h. The METH concentrations in the air in the chamber and urine were analyzed by gas chromatography-mass spectrometry. In conditions 1, METH was detected in the urine at a concentration significantly above the cut-off value, which was the screening kit’s detection limit, even after 72–96 h. On the other hand, in conditions 2 and 3, METH was detected in the urine at concentrations below the cut-off value in the first 24 h. The present study was the first to reveal differences in urinary excretion of METH depending on its inhaled amount. When the results were extrapolated to humans, the amount of METH detected in the urine of the passively exposed subjects was extremely small, which was not detectable by the screening kit.