Methamphetamine concentrations in gastric contents and blood after parenteral and oral administration in rats
It is important, yet difficult, to distinguish the route of administration, parenteral or oral, of methamphetamine on postmortem examination. It might be possible to determine the route of administration by comparing the methamphetamine concentrations in the blood and stomach. However, the changes in methamphetamine concentrations in gastric contents and blood after oral and parenteral administration are unknown. Therefore, the time course of the ratio of methamphetamine concentration in gastric contents and blood (the GB ratio) was investigated using rats to which methamphetamine was administered subcutaneously (subcutaneous group) or orally (oral group). The maximum GB ratio and the maximum mean GB ratio in the subcutaneous group were 54.2 and 31.5, respectively. On the other hand, the GB ratio was 6.38-5,749 in the oral group. Therefore, it is difficult to distinguish the route of methamphetamine administration using the GB ratio alone. However, if the time from administration of methamphetamine to death can be proven, and it is less than 3 h, the route of administration could be clearly identified by measuring methamphetamine concentrations in the blood and gastric contents. Moreover, it might be suggested that the GB ratio would not exceed a certain value (54.2 was observed) after parenteral methamphetamine administration in rats.