A Series of 8 Illicit Fentanyl Intoxication Deaths in Infants and Toddlers.

ABSTRACT: We report 8 children younger than 2 years who died from acute illicit fentanyl intoxications in Connecticut between 2020 and 2022.The Connecticut Office of the Chief Medical Examiner (CT OCME) investigates all unexpected, violent, and suspicious deaths in Connecticut. The CT OCME's electronic database was searched for fentanyl deaths by age. All underwent autopsies and toxicology testing.The ages ranged from 28 days to 2 years (mean age, 12 months). The causes of death involved acute fentanyl intoxications with 1 having xylazine, 1 having para-fluorofentanyl, and 1 having cocaine and morphine. All the manners of death were certified as homicide. The postmortem fentanyl blood concentrations ranged from 0.40 to 46 ng/mL. Most of the children were found unresponsive after being put to sleep. Three were co-sleeping with adults (2 in bed; 1 on a recliner). There was a known history of parental/caregiver drug abuse in 7 of 8 of the fatalities.We summarize the key investigative, autopsy, and toxicological findings. As illicit fentanyl use increases, there is a potential for infant exposure and death. The investigation and certification of these deaths and the role of intentional administration versus inadvertent exposure due to caregiver neglect in the context of the certification of the manner of death are described.

Review of LC techniques for determination of methadone and its metabolite in the biological samples.

Methadone (MTD) is a synthetic analgesic drug used for treating opioid dependence and effectively used clinically for patients with severe pain. The abuse of MTD may lead to poisoning, disorder in the central nervous system and even death. The regular monitoring of MTD in biological matrices including serum, plasma and urine samples is an effective way to control abuse of MTD. In this manner, the selection of analytical monitoring of MTD in biological matrices is of paramount importance. This study was conducted to review high-performance liquid chromatography (HPLC) techniques carried out on MTD and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in the biological samples during 2015-June 2021.

Planned complex suicide involving combined drug intoxication and femoral catheterization.

Complex planned suicide is characterized by the simultaneous use of two or more methods to ensure that death occurs even if one method fails. The authors present an original combination of two self-killing methods. A 42-year-old cardiologist, with a major depressive syndrome and several suicide attempts, as well as cocaine addiction, was found dead at his home with a femoral catheter inserted in the right femoral artery. The autopsy concluded that death was due to major hemorrhagic process in a context of suicide. Toxicological analyses, performed in peripheral blood by gas chromatography coupled to mass spectrometry and by liquid chromatography-diode array detection, revealed the presence of ethanol (0.13 g/L), cocaine, and metabolites (cocaine: 432 µg/L, benzoylecgonine: 3286 µg/L, ecgonine methyl ester: 1195 µg/L, cocaethylene: 41 µg/L), a potentially lethal concentration of citalopram (1.03 mg/L), toxic concentrations of hydroxyzine (0.11 mg/L), bromazepam (2.06 mg/L), and lidocaine (7.30 mg/L). At the end of these analyses, the death was reclassified as planned complex suicide combining drug intoxication and catheterization of the femoral artery. The authors discuss the main aspects of this case and stress the importance of meticulous analysis of all available evidence: witness reports, victim's medical history and occupation, findings of at-the-scene examination, autopsy, and toxicological analyses, in order to exclude homicide and to understand the sequence of events that led to death.

[The use of biochemical characteristics of cadaveric blood in the forensic diagnosis of lethal poisoning]. / Ispol'zovanie nekotorykh sudebno-biokhimicheskikh pokazatelei trupnoi krovi pri diagnostike letal'nykh otravlenii.

The purpose of the work is the development of mathematical models in the forensic diagnosis of poisonings by the main groups of toxicologically important substances, on the basis of biochemical characteristics of blood. The most informative forensic and biochemical indicators of cadaveric blood used to detect lethal poisoning are the urea content, total protein content, and the ratio of urea to creatinine. Mathematical models of poisoning can be used to diagnose poisoning with narcotic drugs, psychotropic substances and substitutes of ethyl alcohol.

The prevalence of gamma-hydroxybutyrate (GHB) in motor vehicle drivers and its co-administration with amphetamine type substances (ATS) in Queensland, Australia (2011-2018).

The routine analysis of driver specimens for gamma-hydroxybutyrate (GHB) is rarely performed by toxicology laboratories as the physical and chemical properties of GHB make it unamenable to the screening methods usually employed. The prevalence of the drug in driver populations has therefore only rarely been reported. This study outlines the results of the routine analysis for GHB in the blood of motor vehicle drivers in Queensland, Australia, over an eight-year period (2011-2018). The methodology for GHB analysis was updated over the course of the study; screening for GHB was conducted using GC/FID or GC/MS between 2011 and 2016 and by LC/MS/MS from 2017 onwards. Due to the endogenous nature of GHB, any specimens containing greater than 5mg/kg GHB were subjected to quantitative analysis by either; GC/MS after liquid-liquid extraction and derivatisation with BSTFA+1%TMCS (2011-2016), or by LC/MS/MS analysis after solvent precipitation from 2017 onwards. Of the 15,061 specimens analysed, 160 were positive for GHB (1.1% of all cases, range 0.4-1.8%). GHB positive drivers were 66.9% male (33.1% female) and had an average age of 32 years. The mean GHB concentration identified was 89mg/kg (range 6-354mg/kg). GHB was found to be closely associated with amphetamine type substances (ATS), particularly methylamphetamine. Though GHB was present in only 2.2% of all ATS positive specimens submitted to the laboratory, 91.2% of all GHB positive cases contained an ATS. Other drugs commonly co-administered with GHB were THC, cocaine, benzodiazepines and erectile dysfunction drugs. GHB was found to be more commonly identified in drivers from city areas and a geographical localisation of the use of the drug was identified in the Gold Coast region of Queensland.

Testing for midazolam and oxycodone in blood after formalin-embalmment: About a complex medico-legal case.

The stability of compounds in formalin solution is an important factor for drug analysis in a toxicological investigation. In this article, the authors report a complex medico-legal case involving midazolam and oxycodone. The complexity of this case comes from the fact that the body was embalmed with formalin solution before the autopsy. This technique, called thanatopraxy, allows the preservation of corpses from decomposition, the destruction of a maximal number of micro-organisms, and the presentation of the body with a natural appearance to the family. Unfortunately, when thanatopraxy is performed before the collection of biological specimens, the toxicological results are not representative of the time of the death. In addition, the interpretation of the results is difficult, because formalin can cause oxidation of xenobiotics present in the body at the time of the death, alter the pH of the tissues and dilute the compounds. To document the chemical stability of midazolam and oxycodone in formalin solution and interpret the results, a stability study was conducted for 21 days. Blood containing midazolam and oxycodone was spiked with formalin, kept at 4°C and regularly tested for both drugs. This study showed a rapid degradation of midazolam and oxycodone (85% during the first 24 hours for oxycodone). In the peripheral blood of the victim, methanol (1.31 g/L), midazolam (74ng/mL) and oxycodone (152 ng/mL) were identified. According to the stability study, the measured concentrations in formalin fixed-tissues are to be interpreted very carefully, knowing that significant degradation has occurred.

Simultaneous determination of cocaine, ecgonine methyl ester, benzoylecgonine, cocaethylene and norcocaine in dried blood spots by ultra-performance liquid chromatography coupled to tandem mass spectrometry.

Cocaine (COC) is one of the most widely abused drugs in the world and its sensitive and its reliable measurement in blood is of great importance in the field of forensic and clinical toxicology. Additionally, the determination of COC metabolites such as benzoylecgonine (BZE), cocaethylene (CE), ecgonine methyl ester (EME), and norcocaine (NCOC) are also of complementary diagnostic value. The quantification of COC and metabolites in dried blood spots (DBS) may be an alternative to conventional collection methods with several advantages, including easier, on-site, collection, transportation and storage. In this study, we present a simple and comprehensively validated UPLC-MS/MS assay to measured COC, BZE, EME, NCOC and CE in DBS. The evaluated assay was linear from 5-500 ng mL-1. Precision assays presented CV% of 1.27-6.82, and accuracy in the range of 97-113.78%. Low haematocrit values had a negative impact in the assay accuracy. COC, BE, NCOC and CE measurements can be made reliably in DBS stored for 14 days at room temperature, as well as at -20 °C and 45 °C. All evaluated compounds can be measured in DBS maintained at -20 °C for 14 days. DBS sampling can be used for the clinical evaluation of the exposure to COC, being an alternative for collection, short-term storage and transportation of blood at room and high temperatures.

Five Postmortem Case Reports with Qualitative Analysis of Cyclopropylfentanyl by LC-MS-MS.

In January 2018, the Drug Enforcement Agency temporarily designated cyclopropylfentanyl as a Schedule I drug. Over the course of 5 months (December 2017-May 2018), the Nassau County Medical Examiner Toxicology Laboratory qualitatively identified and confirmed cyclopropylfentanyl in specimens obtained from five postmortem cases. We describe the five cases and include pertinent autopsy findings and decedent histories, along with results for cyclopropylfentanyl determined in postmortem cardiac blood. Samples were prepared by an alkaline liquid-liquid extraction, with sample pH adjusted to >9 and utilizing an extraction solvent consisting of 90:10 hexane:ethyl acetate. Instrumental analysis was achieved via liquid chromatography tandem mass spectrometry with a dual jetstream electrospray source operating in positive ion mode. Two ion transitions were monitored for each analyte of interest and the internal standard. The estimated concentration range of cyclopropylfentanyl in the reported cases was 5.6 to 82 ng/mL for five postmortem cardiac blood specimens. All five cases included cyclopropylfentanyl in the established cause of death.

Proactive drugs in DFSA cases: Toxicological findings in an eight-years study.

In case of drug-facilitated sexual assault (DFSA), the evidence is frequently anecdotal, with few investigations based on scientific evidences being carried out and thus most cases are diagnosed as an acute drug or alcohol intoxication. The reason may lay in the lack of specific knowledge by the victim on the possibility to retrospectively study the allegedly events and to the absence of standardized and shared protocols among health, forensic and police subjects. On this basis, in 2015 the Unit of Forensic Toxicology of University of Florence and the Sexual Assaults Centre in Hospital Careggi have fixed a common protocol to be applied in case of DFSA. The purpose of the study was to describe the results of the application of the shared protocol for toxicological findings among women seeking health care after sexual assault, and to assess the relationship with so-called proactive DFSA drugs. We conducted a study on female patients above 18 years of age consulting the Sexual Assault Centre between 2010 and July 2018. Among the 256 patients included, 37.1% was positive at least for a substance. Alcohol was the most detected substance (57 cases), followed by Cannabis (19 cases), cocaine (15 cases) and opiates/methadone (heroine: 5; morphine:1; methadone: 6); benzodiazepines and amphetamine were found in 13 and in 2 cases, respectively. Only case of gamma-hydroxybutyrate (GHB) consumption was observed while new psychoactive substances were not detected. Among the patients suspecting proactive DFSA, sedative drug findings, not explained by voluntary intake, were encountered.

Simultaneous determination of drugs and pesticides in postmortem blood using dispersive solid-phase extraction and large volume injection-programmed temperature vaporization-gas chromatography-mass spectrometry.

A d-SPE protocol followed by gas chromatography-mass spectrometry (GC-MS) analysis using large volume injection-programmed temperature vaporization (LVI-PTV) was optimized for simultaneous quantification of 14 pesticides, drugs of abuse, prescription drugs and metabolites in human postmortem blood without derivatization. The validated method showed good repeatability, linearity, intermediate precision, and recovery. LOQs were 0.02 or 0.03µg/mL. The method showed to be fast and easy-to-implement in a forensic laboratory and was satisfactorily applied for the analysis of 10 postmortem blood real samples. Six samples contained cocaine (0.04-3.13µg/mL), two 3,4-methylenedioxymethamphetamine hydrochloride (MDMA, 0.04-0.09µg/mL) and two carbamazepine (0.08-0.98µg/mL). Other analytes found were carbofuran (27.3µg/mL), the metabolite 7-aminoflunitrazepam (1.12µg/mL), amitriptyline (0.21µg/mL) and diazepam (0.03µg/mL).

Single stab injuries.

Determining the manner of death in cases involving multiple stab injuries from a knife is generally straightforward. The medico-legal investigation of a stabbing death caused by a single stab injury from a knife comprises a smaller but potentially more problematic subset of forensic cases. We reviewed our institute's experience with single stab injuries and endeavored to identify features identified at the post-mortem examination which may aid in the differentiation between cases of homicide, suicide and accidental death. The single stab injury was to the left chest in the majority of deaths from homicide and from suicide. Clothing was nearly always involved in cases of homicide, but was also seen in cases of suicide. The knife was found in situ in 9 of the 11 cases of suicide involving a chest injury, but was not seen in any of the cases of homicide. There were no cases of an accidental single stab death from a knife in our records. Clinical data on accidental stab injuries was sought via a search of the medical records of a major tertiary referral hospital. A single non-fatal case of an accidental single stab injury from a knife was identified after the conclusion of our study period. Accidental stab injuries from a knife causing injury or death are rare.

Critical analysis of forensic cut-offs and legal thresholds: A coherent approach to inference and decision.

In this paper we critically discuss the definition and use of cut-off values by forensic scientists, for example in forensic toxicology, and point out when and why such values - and ensuing categorical conclusions - are inappropriate concepts for helping recipients of expert information with their questions of interest. Broadly speaking, a cut-off is a particular value of results of analyses of a target substance (e.g., a toxic substance or one of its metabolites in biological sample from a person of interest), defined in a way such as to enable scientists to suggest conclusions regarding the condition of the person of interest. The extent to which cut-offs can be reliably defined and used is not unanimously agreed within the forensic science community, though many practitioners - especially in operational laboratories - rely on cut-offs for reasons such as ease of use and simplicity. In our analysis, we challenge this practice by arguing that choices made for convenience should not be to the detriment of balance and coherence. To illustrate our discussion, we will choose the example of alcohol markers in hair, used widely by forensic toxicologists to reach conclusions regarding the drinking behaviour of individuals. Using real data from one of the co-authors' own work and recommendations of cut-offs published by relevant professional organisations, we will point out in what sense cut-offs are incompatible with current evaluative guidelines (e.g., [31]) and show how to proceed logically without cut-offs by using a standard measure for evidential value. Our conclusions run counter to much current practice, but are inevitable given the inherent definitional and conceptual shortcomings of scientific cut-offs. We will also point out the difference between scientific cut-offs and legal thresholds and argue that the latter - but not the former - are justifiable and can be dealt with in logical evaluative procedures.

Analysis of Fentanyl and 18 Novel Fentanyl Analogs and Metabolites by LC-MS-MS, and report of Fatalities Associated with Methoxyacetylfentanyl and Cyclopropylfentanyl.

Methoxyacetylfentanyl and cyclopropylfentanyl are two of the newest illicit opioids that are infiltrating the heroin market. Methoxyacetylfentanyl and cyclopropylfentanyl were reported by the Drug Enforcement Administration (DEA) in their third quarter report of 2017 to have been chemically identified seven and five times, respectively, from drug evidence analyzed by the DEA's lab system; Q3 was the first time cyclopropylfentanyl was identified by the DEA's lab system, while methoxyacetylfentanyl was reported one time in Q2 2017. A method was developed using liquid chromatography tandem mass spectrometry for the quantitation of fentanyl, norfentanyl and 17 fentanyl analogs: furanylfentanyl, butyrylfentanyl, despropionylfentanyl (4-ANPP), methoxyacetylfentanyl, tetrahydrofuran fentanyl, fluoro-isobutyrylfentanyl, acrylfentanyl, para-fluorofentanyl, ortho-fluorofentanyl, carfentanil, beta-methylfentanyl, isobutyrylfentanyl, para-methylfentanyl, cyclopentylfentanyl, cyclopropylfentanyl, beta-hydroxyfentanyl and alpha-methylfentanyl. The calibration range for all compounds was 0.1-100 ng/mL. Blood samples from 42 postmortem cases involving cyclopropylfentanyl and methoxyacetylfentanyl from Florida, Illinois, Michigan and Tennessee were submitted for toxicological analysis. The mean and median concentration for the cases testing positive for cyclopropylfentanyl (n = 32) was 15.3 (±11.9) ng/mL and 12.3 ng/mL, respectively, with a range of 1.4-43.3 ng/mL. The mean (±SD) and median concentrations for the 11 cases quantitatively confirmed (3 cases were below the limit of quantitation) for methoxyacetylfentanyl was 17.7 (±11.4) ng/mL and 15.1 ng/mL respectively, with a range of 0.21-39.9 ng/mL. These novel illicit substances typically are outside the scope of routine drug testing by hospitals and toxicology laboratories or below the sensitivity levels for the detection of these substances in biological specimens. These compounds have not previously been studied in humans; therefore, it is significant to be able to associate the pharmacological effects derived from case reports to the quantitative values found in the postmortem specimens.

Epidemiological Study of Carbon Monoxide Deaths in Scotland 2007-2016.

Carbon monoxide (CO) intoxications are quite frequent in forensic toxicology. Using a sample of 209 CO-positive deaths in Scotland from 2007 to 2016, this study provides ranges of percentage CO saturations (%COHb) according to the CO source and examines any correlation with age, gender, alcohol, and preexisting disease. It also reports the full toxicological findings, including drug concentrations, in CO-positive cases. The highest numbers of fatalities involved males, occurred during autumn/winter, and the main source of CO was fire. The median %COHb in fire-related cases was significantly lower than in non-fire-related cases such as those involving exhausts, generators and gas supply systems, and portable BBQs. There was no relationship between %COHb and age, blood alcohol concentration, or the presence of preexisting cardiovascular and/or respiratory disease. Toxicology results revealed that prescription medications were the most commonly detected drug group and that the number of cases positive for controlled drugs was small.

The Use of Serum Methadone/Metabolite Ratios to Monitor Changing Perinatal Pharmacokinetics.

OBJECTIVES: Pregnancy profoundly alters drug metabolism, accelerating clearance and confounding medication management, primarily through induction of CYP450 enzymes. Methadone is a CYP450 substrate with altered pharmacokinetics during pregnancy. We report on the use of serum methadone/metabolite ratios (MMRs) to monitor changes in methadone metabolism through the perinatal period and to objectively guide methadone dosing. Previous research found average MMRs in nonpregnant populations of between 11.3 and 12.7. METHODS: Serum methadone and its major metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine concentrations were analyzed in 67 samples from 23 pregnant patients treated for opioid use disorder, and their calculated ratio was used to document changes in methadone clearance across trimesters and postpartum. Lower ratios indicate increased clearance. RESULTS: The average MMR during pregnancy was 6.1. Ratios declined significantly from trimester 1 to trimester 3 (P = 0.007), and then rose significantly from trimester 3 to postpartum (P = 0.001). The per cent of ratios that were 4 or less, indicating ultrarapid metabolism, increased from 8% to 30% to 38% across trimesters, and decreased to 5% postpartum. Forty-four per cent of individual patients had at least 1 prepartum ratio of 4 or less. CONCLUSIONS: This study documents significant metabolic changes occurring perinatally, which indicate the need for both changes in methadone dose and dose frequency to maintain maternal/fetal stability, and also dose reductions as hypermetabolism reverses postpartum. MMRs provide an objective tool to more efficiently improve the safety and efficacy of methadone dosing perinatally.

Metabolites of Heroin in Several Different Post-mortem Matrices.

In some forensic autopsies blood is not available, and other matrices are sampled for toxicological analysis. The aims of the present study were to examine whether heroin metabolites can be detected in different post-mortem matrices, and investigate whether analyses in other matrices can give useful information about concentrations in peripheral blood. Effects of ethanol on the metabolism and distribution of heroin metabolites were also investigated. We included 45 forensic autopsies where morphine was detected in peripheral blood, concomitantly with 6-acetylmorphine (6-AM) detected in any matrix. Samples were collected from peripheral blood, cardiac blood, pericardial fluid, psoas muscle, lateral vastus muscle, vitreous humor and urine. Opioid analysis included 6-AM, morphine, codeine, and morphine glucuronides. The 6-AM was most often detected in urine (n = 39) and vitreous humor (n = 38). The median morphine concentration ratio relative to peripheral blood was 1.3 (range 0-3.6) for cardiac blood, 1.4 (range 0.07-5.3) for pericardial fluid, 1.2 (range 0-19.2) for psoas muscle, 1.1 (range 0-1.7) for lateral vastus muscle and 0.4 (range 0.2-3.2) for vitreous humor. The number of 6-AM positive cases was significantly higher (P = 0.03) in the ethanol positive group (n = 6; 86%) compared to the ethanol negative group (n = 14; 37%) in peripheral blood. The distribution of heroin metabolites to the different matrices was not significantly different between the ethanol positive and the ethanol negative group. This study shows that toxicological analyses of several matrices could be useful in heroin-related deaths. Urine and vitreous humor are superior for detection of 6-AM, while concentrations of morphine could be assessed from peripheral or cardiac blood, pericardial fluid, psoas muscle and lateral vastus muscle.

Driving under the influence of alcohol and drugs in the eastern part of Denmark in 2015 and 2016: Abuse patterns and trends.

OBJECTIVES: The objective of this study was to examine the frequency of psychoactive drugs and alcohol in drivers under suspicion of driving under the influence of drugs and alcohol in 2015 and 2016 in the eastern part of Denmark. The trends in the number of traffic cases sent for drug analysis since 2000 and alcohol analysis since 2011 are also discussed. METHODS: Blood samples from drivers suspected of being under the influence of alcohol and/or medication and/or illicit drugs in 2015 and 2016 were investigated as requested by the police. The blood samples were screened for alcohol and/or tetrahydrocannabinol (THC) alone, for other drugs (covering all drugs, except THC, listed in the Danish list of narcotic drugs), or for THC and other drugs. Age and gender were also recorded. The number of drug traffic cases since 2000 and the number of alcohol cases since 2011 were extracted from our Laboratory Information Management System (LIMS). RESULTS: In total, 11,493 traffic cases were investigated. Alcohol and/or drugs exceeded the legal limit in 9,657 (84%) cases. Men constituted 95% of the drivers investigated for drugs and 88% of the alcohol cases. The drivers investigated for drugs consisted primarily of young men, whereas drivers investigated for alcohol were older. The frequency was higher for positive alcohol cases above the legal limit (87%) than for drug cases (76%) above the fixed concentration limit. THC (67-69%) was the most frequently detected drug above the legal limit, followed by cocaine (27-28.5%), amphetamine (17%), and clonazepam (6-7%) in both years. Morphine (5.4%), included among the 5 most frequent drugs in 2015, was replaced by methadone (4.6%) in 2016. Few new psychoactive drugs (NPS) were detected. The number of traffic cases sent for drug analysis has increased more than 30-fold since 2000-2006, and the number of traffic cases submitted in 2016 for drug analysis was higher than the number for alcohol analysis; the latter has decreased since 2011. CONCLUSION: Overall, alcohol was the most frequent compound detected above the legal limit in both years, followed by the well-known illicit drugs THC, cocaine, and amphetamine. NPS were seldom seen. One consequence of the increased focus on drugs in traffic has been an immense increase in drug traffic cases sent for analysis since 2006 in the eastern part of Denmark. Although this survey revealed only minimal changes compared to earlier investigations, surveys like this are invaluable for monitoring abuse patterns and trends in drugged and drunken driving.

The Effect of Lowering the Legal Drink-Drive Limit on the Toxicological Findings in Driver Fatalities: A Comparison of Two Jurisdictions.

In December 2014, the legal blood alcohol limit for drivers in both Scotland and New Zealand was reduced from 80 to 50 mg/100 mL. This paper reports a retrospective study comparing changes in the toxicological findings in deceased drivers and motorcyclists before and after the limit change in both jurisdictions. A year of fatal motor vehicle crashes prior to and following the limit change is examined for both countries. In Scotland, there was an increase in drug prevalence among fatally injured drivers and motorcyclists, with the use of all drug groups increasing after the limit change, with the exception of cannabinoids. In New Zealand, there was a reduction in cases involving drugs only, but increases in the numbers of deceased drivers and motorcyclists positive for alcohol only and co-using alcohol and drugs.

Silibinin affects the pharmacokinetics of methadone in rats.

The aim of the present study was to investigate the pharmacokinetic effect of silibinin on methadone in rats. Twenty-four male Sprague-Dawley rats were randomly divided into 4 groups: control group, single dose of 100 mg/kg group, multiple doses of 100 mg/kg group, and multiple doses of 30 mg/kg group. A single dose of 6 mg/kg methadone was administrated to rats orally without or with silibinin. Plasma samples were collected via tail vein at different time points and concentrations of methadone and its metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), were determined by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Compared with the control group (without silibinin), both 30 and 100 mg/kg silibinin significantly increased the Cmax of methadone, but only 100 mg/kg silibinin significantly increased the AUC(0-t) of methadone and decreased its clearance. Pharmacokinetics parameters of EDDP were not altered by 30 mg/kg silibinin; its Tmax was decreased by 100 mg/kg silibinin and the Cmax was increased by single dose of 100 mg/kg silibinin. It is concluded that silibinin significantly altered the pharmacokinetics of methadone in rats by increasing the exposure of methadone. Further investigations in human should be conducted. Therapeutic drug monitoring of methadone in individuals undergoing methadone maintenance therapy is recommended when silibinin is concomitant.