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ABSTRACT: Drug-induced arrhythmia is an adverse drug reaction that can be potentially fatal since it is mostly related to drug-induced QT prolongation, a known risk factor for Torsade de Pointes and sudden cardiac death (SCD). Several risk factors have been described in association to these drug-induced events, such as preexistent cardiac disease and genetic variation. Our objective was to study the genetic susceptibility in pharmacodynamic and pharmacokinetic pathways underlying suspected drug-induced arrhythmias and sudden unexplained deaths in 32 patients. The genetic component in the pharmacodynamic pathway was studied by analysing 96 genes associated with higher risk of SCD through massive parallel sequencing. Pharmacokinetic-mediated genetic susceptibility was investigated by studying the genes encoding cytochrome P450 enzymes using mediumthroughput genotyping. Pharmacodynamic analysis showed three probably pathogenic variants and 45 variants of uncertain significance in 28 patients, several of them previously described in relation to mild or late onset cardiomyopathies. These results suggest that genetic variants in cardiomyopathy genes, in addition to those related with channelopathies, could be relevant to drug-induced cardiotoxicity and contribute to the arrhythmogenic phenotype. Pharmacokinetic analysis showed three patients that could have an altered metabolism of the drugs they received involving CYP2C19 and/or CYP2D6, probably contributing to the arrhythmogenic phenotype. The study of genetic variants in both pharmacodynamic and pharmacokinetic pathways may be a useful strategy to understand the multifactorial mechanism of drug-induced events in both clinical practice and forensic field. However, it is necessary to comprehensively study and evaluate the contribution of the genetic susceptibility to drug-induced cardiotoxicity. (AU)

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Actualmente el fluido oral (FO) es aceptado como una matriz biológica alternativa para detectar drogas en toxicología clínica y forense. En países como Argentina donde el uso de hojas de coca (mascar hojas de coca o beber té de coca) es legal son necesarios procedimientos adecuados para logar una clara diferenciación entre los individuos que usan las hojas de coca de manera legal de aquéllos que usan cocaína en forma ilegal. Poca es la información que hay en la literatura sobre el perfil de los alcaloides de la hoja de coca en FO de personas que mascan hojas de coca o toman té de coca y hasta el presente trabajo no se hallaron datos sobre el perfil en FO de la higrina (HIG) y cuscohigrina (CUS). De este estudio preliminar participaron dos voluntarios. Los resultados mostraron que la CUS e HIG siguieron siendo positivas después que la cocaína (COC) y benzoilecgonina (BE) cayeron por debajo de los valores cut- off propuestos por las guías internacionales para FO en casos de screening (15 a 20 ng/ mL) y de confirmación (8 a 10 ng/mL) en el caso del mascador de coca. En el participante que tomó una taza de té de coca, en el último punto examinado (1 h) resultó ser positivo para la COC y BE y también para la CUS e HIG. El FO podría ser una muestra útil para confirmar el uso legal de la hoja de coca, aun cuando futuros estudios son necesarios para corroborar estos primeros datos.

Nowadays oral fluid (OF) is accepted as an alternative biological sample for detecting drugs in clinical and forensic toxicology. In countries like Argentina, where the use of coca leaves (coca leaves chewing and coca tea drinking) is legal, adequate procedures are required to allow a clear differentiation between people who use coca leaves (legal practice) and those who use cocaine (illicit practice). There is scarce literature regarding coca leaf alkaloids profile in OF from people who chew coca leaves and drink coca tea. Until now, coca leaf alkaloids profile of hygrine (HYG) and cuscohygrine (CUS) in OF were not described in the literature. The current preliminary study was performed with two healthy volunteers. In this research CUS and HYG have been found to be positive (detectable) even when cocaine (COC) and benzoylecgonine (BE) are dropped below the cut-off values proposed by international guidelines for screening (15 to 20 ng/mL), and confirmation (8 to 10 ng/mL) in OF. In addition, CUS and HYG were also found to be positive at the same time of the last detection of COC and BE after coca tea consumption. The OF would be a useful sample to confirm the legal use of coca leaf, even when more researches are therefore needed.

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Cocaine abuse is widespread all over the world, and is performed generally by sniffing, injecting or smoking cocaine or crack. The distinction between the recreational use of cocaine from the practice of the so called "coqueo" is still an issue in those countries where this habit is diffused and where it is not considered an addiction, by this reason is necessary to develop a method for to distinguish the coca chewers and cocaine abusers. The use of an unique marker to distinguish between cocaine abuse and chewing of coca leaves is of fundamental importance in those countries where this habit is diffused. Certain alkaloids of the leaves of Erythroxylum coca are lost during the process of extraction/purification of cocaine and it is not possible to find them neither in seizures of chlorhidrate of cocaine nor urine samples of cocaine abusers. These markers are the hygrine and cuscohygrine that are present in the leaves of E. coca. A fast GC/MS method involving a liquid:liquid extraction procedure with tertbutylmethylether (TBME) is proposed for the determination of some alkaloids in cocaine leaves, cocaine seizures and biological samples. All specimens were alkalinized to pH 9 with a carbonate/bicarbonate buffer and then extracted with TBME. The analysis was carry out by GC/MS with electron impact at 70 eV and in full scan mode. The results demonstrate that hygrine and cuscohygrine are not found neither in the urine of cocaine abusers nor in cocaine seizures. For this reason this compounds could be considered as markers of coca chewing. This developed method permits to distinguish coca chewing from cocaine abuse in workplace drug testing through the analysis of urine samples.

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Solid-phase microextraction (SPME) is a new extraction technique with many advantages: small sample volume, simplicity, quickness and solvent-free. It is mainly applied to environmental analysis, but is also useful for the extraction of drugs from biological samples. In this paper the use of SPME is proposed for the determination of methadone and its main metabolite EDDP in hair by GC-MS. The hair samples were washed, cut into 1-mm segments, and incubated with Pronase E for 12 h. A 100-micron polydimethylsiloxane (PDMS) film fibre was submerged for 30 min in a diluted solution of the hydrolysis liquid (1:4 with borax buffer) containing methadone-d3 and EDDP-d3 as internal standards. Once the microextraction was concluded the fibre was directly inserted into the CG injection port. Linearity was found for methadone and EDDP in the range studied, 1.0-50 ng/mg hair, with correlation coefficients higher than 0.99. Interassay relative standard deviation (R.S.D) was determined to be less than 13.30% for methadone and less than 8.94% for EDDP, at 3.0 and 30.0 ng/mg. Analytical recoveries were close to 100% for both compounds on spiked samples. The method was applied to the analysis of real hair samples from eight patients of a methadone maintenance programme. The concentration of methadone in hair ranged from 2.45 to 78.10 ng/mg, and for EDDP from 0.98 to 7.76 ng/mg of hair.

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The evaluation of drug abuse in a defined population was performed through toxicological hair analysis. Hair samples from university students ranging from 18 to 25 years of age were anonymously collected and screened for cocaine, amphetamines and cannabinoids by radioimmunoassay (RIA). Positive results (cut-off values adopted were 2 ng/mg for cocaine and amphetamines and 0.5 ng/mg for cannabinoids) were confirmed by GC/MS. Preliminary results showed 19% of positive results for cocaine on 200 samples analysed. No confirmed positive results were obtained for amphetamine analysis. RIA technique demonstrated its unsuitability for cannabinoids preliminary screening on hair, giving a high percent of false positive results.

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