Study On The Forensic Toxicokinetics Of Phenobarbital

Objective1.To establish the analysis of the phenobarbital in living samples by a GC and a GC/MS.2.To develop a toxicokinetics and dynamic distribution,postmortem distribution and postmortem redistribution model of phenobarbital in rats.3.Study the toxicokinetics, dynamic distribution, postmortem distribution and postmortem redistribution of phenobarbital in rats, and provide a scientific evidence for the forensic identification of phenobarbital poisoning death.Methods1.GC/MS and GC: The samples including blood and tissues, to which internal standard object (allobarbital) was added, were acidified to pH1², and extracted with ether. The extract was analyzed qualitatively and quantitatively by GC/MS and GC respectively with an internal standard and working curve method.2.The toxicokinetics and dynamic distribution of phenobarbital in rats: 54 male winster rats were given phenobarbital through stomach with a dose of 330 mg·kg^-1. The specimens such as heart, liver, spleen, lung, kidney, and brain of rats were collected at 1,5,10,15,20,30,48,72,96h and analyzed by by GC/MS and GC equipped with NPD.3.The postmortem distribution of phenobarbital: 12 male wistar rats were randomly allocated to LD50 and 2LD50 groups, which were given an intragastric administration of phenobarbital with a dose of 0.66 mg·kg^-1 or 1.32 mg·kg^-1. As soon as the vital signs disappeared, the rats were dissected and the specimens such as heart blood, heart liver,spleen,lung,kidney,brain,stomach, were sampled immediately, in which the concentration of Phenobarbital was determined by a GC and a GC/MS.4.The postmortem redistribution of phenobarbital: Phenobarbital with a dose of 330 mg·kg^-1 was administered orally to 54 male wistar rats, The rats were put to death for 10 hours after administration, then placed at 20℃, The heart-blood, heart, liver, lung, kidney, spleen, muscle,brain was taken at different time point of 0h, 2h, 4h, 8h, 12h, 24h, 48h, 72h, 96h after the death respectively, qualitative and quantitative analysis was performed by a GC/MS and a GC equipped with a NPD.5.Statistics method:The datas was collected by software SPSS11.5 and expressed by .Results1.GC/MS and GC:The m/z of characteristic ion of phenobarbital was 204,232 by a GC/MS. The linear range of phenobarbital in biomaterial by a GC was 0.5 to 280μg·mL^-1 orμg·g^-1. The regression equation, linear range, correlation coefficient, recovery , limit of detection of phenobarbital in heart blood was Y = 43.476X + 0.8168(μg·mL^-1), 0.5 -280μg·mL^-1, 0.9955, 97.50±2.0%,0.5μg·mL^-1; and in liver was Y = 46.867X + 0.0884 (μg·g^-1), 0.5 -280μg·g^-1, 0.994, 98.5±3.5%, 0.5μg·g^-1 respectively.2.Toxicokinetics and dynamic distribution: The toxicokinetics of Phenobarbital in rats with a dose of 330 mg·kg^-1 conform to single compartment open model with a first order processes by intragastric administration. Every organs conform to single compartment open model with a first order processes by intragastric administration. Tmax was 7.39h and T1/2k10 was 26.02h in heart blood, tmax was 2.41h⁴.73h and t1/2k10 was 8.59h²0.91h in every organs. The order of Phenobarbital was liver, heart blood, heart, lung and other organ in rats by intragastric administration.The concentration of phenobarbital achieved the peak value at 5h after administration, then descended constantly.3.Postmortem distribution: After the administration of phenobarbital, the rats showed less activities, lethargy state. The LD50 group rats died after the administration for7.37h±2.71h, and the 2LD50 did for 1.33h±0.25h. The order of phenobarbital detected in rats was as follows: (1) LD50 group: stomach (1261.34±591.83)> heart (332.88±70.87), brain (289.81±71.43), liver (284.76±79.44), lung (284.58±67.47), spleen (272.56±31.53), heart blood (269.52±44.62) > kidney (156.61±43.72). (2) 2LD50 group: stomach (1649.21±1212.82) > liver (357.83±138.67), brain (323.19±159.92), heart (310.95±130.73), blood ( 309.93±135.60), lung (308.28±134.48), spleen (299.77±104.58) > kidney (233.24±91.92).4.Postmortem redistribution: At 20?C, the phenobarbital concentrations detected in the heart-blood, heart, liver, lung, kidney, spleen, muscle, brain of died rat at 2⁴our after the death is significantly higher than at 0 hour (p<0.05); the phenobarbital concentration detected in the spleens of died rats at 2 hour after the death is significantly higher than at 0 hour (p<0.05).Conclusion1.The GC/MS and GC method is more selective, more sensitive, simpler, more accurate, and can be applied not only to the clinical diagnosis of phenobarbital poisoning, but also to forensic identification of phenobarbital poisoning death.2 . To develop a toxicokinetics,dynamic distribution, postmortem distribution and postmortem redistribution of Phenobarbital,which apply to study on the forensic toxicokinetics of phenobarbital.3 . The forensic toxicokinetics of phenobarbital in blood and organs meet single compartment open model with a first order processes.The order of phenobarbital in poisoning rats: liver, heart blood, heart, lung, other tissue.The concentrations of phenobarbital reach peak at 5h in organs,then the concentration descent.4.The concentration of phenobarbital in blood was lower than in other organs except for spleen and kidney. So, besides the blood, more organs of poisoning rats should be collected for samples in forensic identification of phenobarbital poisoning death.5.Postmortem redistribution took place.The concentration of phenobarbital take on the tendency of high in organs.