Pitfalls and challenges associated with phenoconversion in forensic toxcicology.

PURPOSE: In recent years, several publications have demonstrated the interest and the usefulness of pharmacogenetics in forensic toxicology. However, this approach remains namely focused on DNA-based phenotype, which may potentially lead to misinterpretation. Other determinants such as co-medication or physiological parameters may also impact the phenotype. This article aims to highlight the importance of considering such determinants in forensic toxicology, through the original case of a heroin-related fatality. METHOD: Ethanol concentration determination and toxicological screening were performed using gas chromatography with flame ionization detection, liquid chromatography with diode array detection and gas chromatography with mass spectrometry detection. CYP2C19 and CYP2D6 genotypes were determined by Taqman® real-time PCR analyses. RESULTS: Femoral blood analyses revealed the presence of ethanol, morphine, codeine, venlafaxine (VEN), O-desmethylvenlafaxine (ODV) and N-desmethylvenlafaxine (NDV), paroxetine, and risperidone. 6-acetylmorphine was also identified in urine. VEN, paroxetine and risperidone were quantified at supra-therapeutic or toxic blood concentrations. NDV was not quantified. The metabolic ratio of VEN (ODV to VEN) was exceptionally low (about 0.7). Pharmacogenetics testing showed that the patient was heterozygous for the CYP2C19*2 loss-of-function allele, which predict an intermediate metabolism for CYP2C19. None of the deficient CYP2D6 alleles investigated were identified. Those results suggest an extensive CYP2D6-metabolism phenotype. CONCLUSION: A discrepancy was seen between the results of the genomic evaluation and the observed metabolic ratio of VEN. This tends to exclude a genetic origin and lead us to formulate other hypotheses, such as phenoconversion that may have been induced by drug interaction involving patients' regular medications. Phenoconversion is as a complex phenomenon that leads to genotype-phenotype mismatch without any genetic abnormality particularly described for cytochromes P450 2D6 and 2C19. Although transient, phenoconversion can have a significant impact on the analysis and interpretation of genotype-focused clinical outcomes correlation and in forensic toxicology conclusions.

Baclofen overdose following recreational use in adolescents and young adults: A case report and review of the literature.

Over the past twenty years, psychotropic drug abuse by young people, especially by teenagers, has received special attention. Here, we present the case of baclofen overdose in a 16-year-old male who recreationally, and probably recurrently, self-administered baclofen. In addition, a review of other cases was conducted. The 16-year-old boy presented to emergency department with digestive signs followed by agitated confusion. Detection and determination of baclofen concentration were achieved using liquid chromatography tandem mass spectrometry. Baclofen was detected in plasma and urine, at 420 ng/mL and 64 900 ng/mL respectively. Further, an English exhaustive literature search was performed using several different scientific databases without any limiting period in order to identify scientific articles dealing with baclofen overdose following a recreational use among adolescent and young adults. Five publications describing baclofen overdoses following a recreational use among adolescents and young adults have been published reporting19 cases, all involving a non-fatal overdose, with baclofen concentrations ranging from less than 20-1322 ng/mL. Baclofen is a psychotropic drug and its recreational use among adolescents and young adults represent a serious problem and should be considered by healthcare professionals. Among young people, baclofen poisoning remains relatively infrequent or most likely underestimated and these observations highlight the importance of constructive communication and joining efforts of clinicians and analytical toxicologists.

Pharmacokinetic analysis of pralidoxime after its intramuscular injection alone or in combination with atropine-avizafone in healthy volunteers.

BACKGROUND AND PURPOSE: Treatment of organophosphate poisoning with pralidoxime needs to be improved. Here we have studied the pharmacokinetics of pralidoxime after its intramuscular injection alone or in combination with avizafone and atropine using an auto-injector device. EXPERIMENTAL APPROACH: The study was conducted in an open, randomized, single-dose, two-way, cross-over design. At each period, each subject received either intramuscular injections of pralidoxime (700 mg), or two injections of the combination: pralidoxime (350 mg), atropine (2 mg), avizafone (20 mg). Pralidoxime concentrations were quantified using a validated LC/MS-MS method. Two approaches were used to analyse these data: (i) a non-compartmental approach; and (ii) a compartmental modelling approach. KEY RESULTS: The injection of pralidoxime combination with atropine and avizafone provided a higher pralidoxime maximal concentration than that obtained after the injection of pralidoxime alone (out of bioequivalence range), while pralidoxime AUC values were equivalent. Pralidoxime concentrations reached their maximal value earlier after the injection of the combination. According to Akaike and to goodness of fit criteria, the best model describing the pharmacokinetics of pralidoxime was a two-compartment with a zero-order absorption model. When avizafone and atropine were injected with pralidoxime, the best model describing pralidoxime pharmacokinetics becomes a two-compartment with a first-order absorption model. CONCLUSIONS AND IMPLICATIONS: The two approaches, non-compartmental and compartmental, showed that the administration of avizafone and atropine with pralidoxime results in a faster absorption into the general circulation and higher maximal concentrations, compared with the administration of pralidoxime alone.

Bioavailability of diazepam after intramuscular injection of its water-soluble prodrug alone or with atropine-pralidoxime in healthy volunteers.

BACKGROUND AND PURPOSE: The aim of this study was to assess the relative bioavailability of diazepam after administration of diazepam itself or as a water-soluble prodrug, avizafone, in humans. EXPERIMENTAL APPROACH: The study was conducted in an open, randomized, single-dose, three-way, cross-over design. Each subject received intramuscular injections of avizafone (20 mg), diazepam (11.3 mg) or avizafone (20 mg) combined with atropine (2 mg) and pralidoxime (350 mg) using a bi-compartmental auto-injector (AIBC). Plasma concentrations of diazepam were quantified using a validated LC/MS-MS assay, and were analysed by both a non-compartmental approach and by compartmental modelling. KEY RESULTS: The maximum concentration (C(max)) of diazepam after avizafone injection was higher than that obtained after injection of diazepam itself (231 vs. 148 ng.mL(-1)), while area under the curve (AUC) values were equal. Diazepam concentrations reached their maximal value faster after injection of avizafone. Injection of avizafone with atropine-pralidoxime (AIBC) had no effect on diazepam C(max) and AUC, but the time to C(max) was increased, relative to avizafone injected alone. According to the Akaike criterion, the pharmacokinetics of diazepam after injection as a prodrug was best described as a two-compartment with zero-order absorption model. When atropine and pralidoxime were injected with avizafone, the best pharmacokinetic model was a two-compartment with a first-order absorption model. CONCLUSION AND IMPLICATIONS: Diazepam had a faster entry to the general circulation and achieved higher C(max) after injection of prodrug than after the parent drug. Administration of avizafone in combination with atropine and pralidoxime by AIBC had no significant effect on diazepam AUC and C(max).

Disposition of everolimus in mdr1a-/1b- mice and after a pre-treatment of lapatinib in Swiss mice.

The aim of this study was to document the in vivo transport of everolimus (inhibitor of mTOR) by P-glycoprotein (P-gp), and to investigate the influence of lapatinib (inhibitor of P-gp) on everolimus disposition. Pharmacokinetics of everolimus (0.25mg/kg) has been investigated after oral administration in mdr1a-/1b- mice compared to the wild type. Also, everolimus pharmacokinetics was characterized after oral administration on Swiss mice either alone or after 2 days of pre-treatment of lapatinib (200mg/kg). The influence of lapatinib pre-treatment on intestinal P-gp expression was investigated by Western blot analysis. The non-compartimental analysis was performed using Winonlin professional version 4.1 software (Pharsight, Mountain View, CA). The areas under the plasma concentration-time curve (AUC) were compared using Bailer's method. A significant 1.3-fold increase of everolimus AUC observed in mdr1a-/1b- mice suggested that everolimus is transported in vivo by intestinal P-gp in mice. In addition, a 2.6-fold significant increase of everolimus AUC with lapatinib pre-treatment as compared with the everolimus alone group was noticed. The elimination half-life was comparable (t(1/2)=5.3h vs. t(1/2)=4h). A 38.5% significant decrease of P-gp expression was observed in duodenum segment in lapatinib pre-treated group as compared with control group. In conclusion, lapatinib enhanced everolimus absorption by decreasing intestinal P-gp expression. An inhibition of CYP 450 could not be excluded. These results confirm the necessity of a therapeutic monitoring of everolimus combined with an inhibitor of the P-gp and CYP 450 like lapatinib in a future anti-tumor treatment.