The role of drug efflux and uptake transporters in the plasma pharmacokinetics and tissue disposition of morphine and its main metabolites.

Morphine is a widely used opioid for the treatment of pain. Differences in drug transporter expression and activity may contribute to variability in morphine pharmacokinetics and response. Using appropriate mouse models, we investigated the impact of the efflux transporters ABCB1 and ABCG2 and the OATP uptake transporters on the pharmacokinetics of morphine, morphine-3-glucuronide (M3G), and M6G. Upon subcutaneous administration of morphine, its plasma exposure in Abcb1a/1b-/-;Abcg2-/--, Abcb1a/1b-/-;Abcg2-/-;Oatp1a/1b-/-;Oatp2b1-/- (Bab12), and Oatp1a/1b-/-;Oatp2b1-/- mice was similar to that found in wild-type mice. Forty minutes after dosing, morphine brain accumulation increased by 2-fold when mouse (m)Abcb1 and mAbcg2 were ablated. Relative recovery of morphine in small intestinal content was significantly reduced in all the knockout strains. In the absence of mOatp1a/1b and mOatp2b1, plasma levels of M3G were markedly increased, suggesting a lower elimination rate. Moreover, Oatp-deficient mice displayed reduced hepatic and intestinal M3G accumulation. Mouse Oatps similarly affected plasma and tissue disposition of subcutaneously administered M6G. Human OATP1B1/1B3 transporters modestly contribute to the liver accumulation of M6G. In summary, mAbcb1, in combination with mAbcg2, limits morphine brain penetration and its net intestinal absorption. Variation in ABCB1 activity due to genetic polymorphisms/mutations and/or environmental factors might, therefore, partially affect morphine tissue exposure in patients. The ablation of mOatp1a/1b increases plasma exposure and decreases the liver and small intestinal disposition of M3G and M6G. Since the contribution of human OATP1B1/1B3 to M6G liver uptake was quite modest, the risks of undesirable drug interactions or interindividual variation related to OATP activity are likely negligible.

CYP2B6 and ABCB1 genotypes predict methadone plasma exposure among patients on maintenance therapy against opioid addictions in Tanzania.

AIMS: Methadone maintenance therapy (MMT) exhibits significant variability in pharmacokinetics and clinical response, partly due to genetic variations. However, data from sub-Saharan African populations are lacking. We examined plasma methadone variability and pharmacogenetic influences among opioid-addicted Tanzanian patients. METHODS: Patients attending MMT clinics (n = 119) in Tanzania were genotyped for common functional variants of the CYP3A4, CYP3A5, CYP2A6, CYP2B6, CYP2C19, CYP2D6, ABCB1, UGT2B7 and SLCO1B1 genotypes. Trough plasma concentrations of total methadone, S-methadone (S-MTD) and R-methadone (R-MTD), with their respective metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The methadone-to-EDDP metabolic ratio (MMR) was used to categorize the phenotype. RESULTS: The proportions of MMR-predicted ultrarapid, extensive, intermediate and slow methadone metabolizer phenotypes were 2.5%, 58.2%, 23.7% and 15.6%, respectively. CYP2B6 genotype significantly correlated with S-methadone (P = .006), total methadone (P = .03), and dose-normalized methadone plasma concentrations (P = .001). Metabolic ratios of R-methadone (R-MTD/R-EDDP), S-methadone (S-MTD/S-EDDP), and total methadone (MMR) were significantly higher among patients homozygous for defective variants (*6 or *18) than heterozygous or CYP2B6*1/*1 genotypes (P < .001). The metabolic ratio for S-MTD and total methadone was significantly higher among ABCB1c.3435T/T than in the C/C genotype. No significant effect of CYP2D6, CYP2C19, CYP3A4, CYP3A5, CYP2A6, UGT2B7 and SLCO1B1 genotypes on S-methadone, R-methadone, or total methadone was observed. CONCLUSIONS: Approximately one in six opioid-addicted Tanzanian patients are methadone slow metabolizers, influenced by genetic factors. Both the CYP2B6 and ABCB1 genotypes are strong predictors of methadone metabolic capacity and plasma exposure. Further investigation is needed to determine their predictive value for methadone treatment outcomes and to develop genotype-based dosing algorithms for safe and effective therapy.

Intoxications involving methoxyacetylfentanyl and U-47700: a study of 3 polydrug fatalities.

Novel synthetic opioids (NSOs) represent an emerging group of novel psychoactive substances, acting as agonists at the opioid receptors. NSOs include fentanyl-related compounds, e.g. methoxyacetylfentanyl (MeACF), and non-fentanyl analogs, e.g. "U compounds" including U-47700. Here we present three cases of death involving MeACF and U-47700, with particular reference to preliminary data on pharmacokinetics and tissue distribution.After a complete post-mortem examination, general unknown screenings and analysis of drugs of abuse were performed on postmortem samples by immunoassays, gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. To quantify the analytes of interest in post-mortem blood and tissues, the standard addition method was used. A toxicological significance score (TSS), weighing the role of the NSO in each death case, was assigned.Case 1 died at the hospital after consumption of U-47700, methadone (serum levels: 2,600 ng/ml and 37 ng/ml), tilidine and benzodiazepines. In case 2, U-47700 (204 ng/ml) together with methadone (290 ng/ml), flubromazepam (480 ng/ml) and diazepam (300 ng/ml) were detected in peripheral blood. In case 3, methoxyacetylfentanyl (266 ng/ml), furanylfentanyl (4.3 ng/ml) 4-ANPP (15 ng/ml) and alprazolam (69 ng/ml) were quantified in femoral blood. In all cases, the NSO likely contributed to the death (TSS = 3).NSOs appear to be often consumed in the setting of polydrug intoxications, especially in combination with other opioids and benzodiazepines, which often exert synergistic effects. The standard addition method remains the most reliable in post-mortem analysis and toxicological results should always be evaluated together with circumstantial and autopsy data.

In vitro, in vivo metabolism and quantification of the novel synthetic opioid N-piperidinyl etonitazene (etonitazepipne).

OBJECTIVES: N-piperidinyl etonitazene (etonitazepipne) is a newly synthesized opioid related to the 2-benzylbenzimidazole analog class. Etonitazepipne has been formally notified and placed under intensive monitoring in Europe in January 2022. Nitazenes have high affinity at µ-opioid receptor (MOR). Etonitazepipne, specifically shows a EC50 of 2.49 nM, suggesting about 50 times higher potency combined with higher efficacy compared to morphine. Antinociceptive potency l ('hot plate test' with rats) was 192-fold greater than that of morphine. METHODS: Here we report on a post-mortem case involving etonitazepipne and its quantification using a standard addition method (SAM) through liquid chromatography tandem mass spectrometry (LC-MS/MS). In addition, characterization and identification of phase I human metabolites using in vitro assay based on pooled human liver microsomes (pHLM) was performed along with the analysis of authentic urine samples by means of high-performance liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). RESULTS: The concentration of etonitazepipne in post-mortem blood and urine was 8.3 and 11 ng/mL, respectively. SAM was validated by assessing the following parameters: intraday and interday repeatability, matrix effect and recovery rate in post-mortem blood. A total of 20 and 14 metabolites were identified after pHLM incubation and urine analysis, respectively. Most pronounced in vitro and in vivo transformations were O-deethylation, hydroxylation, ketone reduction, and combinations thereof. CONCLUSIONS: Considering small traces of the parent drug often found in real cases, the identification of metabolic biomarkers is crucial to identify exposure to this drug. O-deethylated, oxidated metabolites, and combination thereof are proposed as urinary biomarkers along with the parent compound.

Fentanyl Deaths in Infants and Children: A Case Series and Literature Review.

ABSTRACT: Death due to fentanyl and its various analogs has resulted in an exponential rise in deaths throughout the United States, overwhelming many medical examiner offices for over a decade. Its potency and prevalence have caused fentanyl to become the most reported substance in overdose fatalities, with an accompanying increase in exposure of the most vulnerable, infants and children. This report provides information about fentanyl in the pediatric population, including case examples, proposed investigative practices, published therapeutic and lethal blood concentrations, and available resources for future cases. Nine cases of pediatric death between 2013 and 2023 due to fentanyl were reviewed. Five case summaries are presented that highlight classic features of fentanyl deaths in infants, children, and teenagers. Deaths due to fentanyl have continued to rise year after year. Infants and children, most of whom are opioid naive, are at ever increased risk for exposure to high levels of fentanyl. The legal ramifications of a positive fentanyl level in a child increase the need for caution on the part of the forensic pathologist. Understanding what can and cannot be proven by autopsy as well as what resources are available to strengthen one's justification for fentanyl being the primary cause of death is critical.

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.

Pharmacokinetics of methadone after intravenous and subcutaneous administration in domestic ferrets (Mustela putorius furo).

OBJECTIVE: To determine the pharmacokinetic profile of methadone after intravenous (IV) and subcutaneous (SC) administration in domestic ferrets (Mustela putorius furo). STUDY DESIGN: Crossover experimental study. ANIMALS: A group of eight healthy adult ferrets weighing 1.01 ± 0.23 kg (mean ± standard deviation). METHODS: Methadone hydrochloride (0.3 mg kg-1) was injected IV or SC to each ferret with a 3 week washout period. Blood samples were collected via a jugular catheter before and 5, 10, 15, 20, 30, 45, 60, 90, 120, 180, 240, 360 and 480 minutes after drug administration. Liquid chromatography-tandem mass spectrometry was used to determine plasma methadone concentrations. A nonlinear mixed effects model was used to analyze the data. RESULTS: After IV injection, systemic clearance (Clss) and volume of distribution (Vdss) were 78.9 mL min-1 kg-1 and 9.8 L kg-1, respectively. Elimination half-life was 2.0 hours and SC bioavailability was fixed at 1. The maximum observed plasma concentration after SC injection was 92.1 ± 76.8 ng mL-1. Behavioral changes were observed after both routes. CONCLUSIONS AND CLINICAL RELEVANCE: The pharmacokinetic profile of IV methadone was characterized by a high Clss and large Vdss, with high bioavailability and absorption rate after SC administration. Half-life was short and mean plasma methadone concentrations stayed above the minimum effective concentration (MEC) reported in humans only after SC administration for 5 minutes, but remained above that reported in dogs for 45 minutes following both routes. Further studies investigating the MEC and pharmacodynamics of methadone in ferrets are warranted.

Physiologically based pharmacokinetic/pharmacodynamic model for the prediction of morphine brain disposition and analgesia in adults and children.

Morphine is a widely used opioid analgesic, which shows large differences in clinical response in children, even when aiming for equivalent plasma drug concentrations. Age-dependent brain disposition of morphine could contribute to this variability, as developmental increase in blood-brain barrier (BBB) P-glycoprotein (Pgp) expression has been reported. In addition, age-related pharmacodynamics might also explain the variability in effect. To assess the influence of these processes on morphine effectiveness, a multi-compartment brain physiologically based pharmacokinetic/pharmacodynamic (PB-PK/PD) model was developed in R (Version 3.6.2). Active Pgp-mediated morphine transport was measured in MDCKII-Pgp cells grown on transwell filters and translated by an in vitro-in vivo extrapolation approach, which included developmental Pgp expression. Passive BBB permeability of morphine and its active metabolite morphine-6-glucuronide (M6G) and their pharmacodynamic parameters were derived from experiments reported in literature. Model simulations after single dose morphine were compared with measured and published concentrations of morphine and M6G in plasma, brain extracellular fluid (ECF) and cerebrospinal fluid (CSF), as well as published drug responses in children (1 day- 16 years) and adults. Visual predictive checks indicated acceptable overlays between simulated and measured morphine and M6G concentration-time profiles and prediction errors were between 1 and -1. Incorporation of active Pgp-mediated BBB transport into the PB-PK/PD model resulted in a 1.3-fold reduced brain exposure in adults, indicating only a modest contribution on brain disposition. Analgesic effect-time profiles could be described reasonably well for older children and adults, but were largely underpredicted for neonates. In summary, an age-appropriate morphine PB-PK/PD model was developed for the prediction of brain pharmacokinetics and analgesic effects. In the neonatal population, pharmacodynamic characteristics, but not brain drug disposition, appear to be altered compared to adults and older children, which may explain the reported differences in analgesic effect.

Rifampin Reduces the Plasma Concentrations of Oral and Intravenous Hydromorphone in Healthy Volunteers.

BACKGROUND: Several opioids are metabolized by the inducible cytochrome P450 (CYP) 3A isozymes. Coadministration with strong inducers of drug metabolism, such as rifampin, can dramatically reduce systemic exposure to these opioids. As the CYP metabolism of hydromorphone is of minor importance, we studied in healthy volunteers whether hydromorphone would be an effective analgesic for patients who concomitantly receive the prototypical enzyme inducer rifampin. METHODS: In this paired, randomized, crossover study, 12 participants received oral placebo or rifampin for 8 days. Oral hydromorphone (2.6 mg) was administered on day 6 followed by intravenous hydromorphone (0.02 mg/kg) on day 8. Hydromorphone and hydromorphone-3-glucuronide (HM3G) plasma concentrations were measured for 24 hours and psychomotor responses, including perceived drug effect, change in pupil diameter, and cold pressor threshold were evaluated for 6 hours. Our primary outcome was the change in the area under the concentration-time curve (AUC0-last) of oral and intravenous hydromorphone after pretreatment with rifampin or placebo. Pharmacodynamic parameters and other pharmacokinetic parameters were analyzed as secondary outcomes. RESULTS: Rifampin reduced the AUC0-last of oral and intravenous hydromorphone by 43% (ratio to control: 0.57, 90% confidence interval [CI], 0.50-0.65) and 26% (ratio to control: 0.74, 90% CI, 0.69-0.79), respectively. The maximum concentration of oral hydromorphone was reduced by 37% (ratio to control: 0.63, 90% CI, 0.55-0.72), and oral bioavailability decreased from 33% to 26% (ratio to control: 0.78, 90% CI, 0.67-0.91) in the rifampin phase compared with placebo. The HM3G-to-hydromorphone ratio increased by 50% (90% CI, 25-79) and 42% (90% CI, 29-55) after oral and intravenous hydromorphone, respectively. Rifampin did not significantly affect the pharmacodynamic parameters. CONCLUSIONS: Rifampin significantly reduces the concentrations of oral and intravenous hydromorphone. This interaction is due to an increase in the first-pass and systemic metabolism of hydromorphone, likely involving induction of uridine 5'-diphospho- glucuronosyltransferase enzymes by rifampin. The enhancement of hydromorphone elimination should be considered when managing pain of patients who are treated with strong enzyme inducers.

A Novel Perioperative Multidose Methadone-Based Multimodal Analgesic Strategy in Children Achieved Safe and Low Analgesic Blood Methadone Levels Enabling Opioid-Sparing Sustained Analgesia With Minimal Adverse Effects.

BACKGROUND: Intraoperative methadone, a long-acting opioid, is increasingly used for postoperative analgesia, although the optimal methadone dosing strategy in children is still unknown. The use of a single large dose of intraoperative methadone is controversial due to inconsistent reductions in total opioid use in children and adverse effects. We recently demonstrated that small, repeated doses of methadone intraoperatively and postoperatively provided sustained analgesia and reduced opioid use without respiratory depression. The aim of this study was to characterize pharmacokinetics, efficacy, and safety of a multiple small-dose methadone strategy. METHODS: Adolescents undergoing posterior spinal fusion (PSF) for idiopathic scoliosis or pectus excavatum (PE) repair received methadone intraoperatively (0.1 mg/kg, maximum 5 mg) and postoperatively every 12 hours for 3-5 doses in a multimodal analgesic protocol. Blood samples were collected up to 72 hours postoperatively and analyzed for R-methadone and S-methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidene (EDDP) metabolites, and alpha-1 acid glycoprotein (AAG), the primary methadone-binding protein. Peak and trough concentrations of enantiomers, total methadone, and AAG levels were correlated with clinical outcomes including pain scores, postoperative nausea and vomiting (PONV), respiratory depression, and QT interval prolongation. RESULTS: The study population included 38 children (10.8-17.9 years): 25 PSF and 13 PE patients. Median total methadone peak plasma concentration was 24.7 (interquartile range [IQR], 19.2-40.8) ng/mL and the median trough was 4.09 (IQR, 2.74-6.4) ng/mL. AAG concentration almost doubled at 48 hours after surgery (median = 193.9, IQR = 86.3-279.5 µg/mL) from intraoperative levels (median = 87.4, IQR = 70.6-115.8 µg/mL; P < .001), and change of AAG from intraoperative period to 48 hours postoperatively correlated with R-EDDP (P < .001) levels, S-EDDP (P < .001) levels, and pain scores (P = .008). Median opioid usage was minimal, 0.66 (IQR, 0.59-0.75) mg/kg morphine equivalents/d. No respiratory depression (95% Wilson binomial confidence, 0-0.09) or clinically significant QT prolongation (median = 9, IQR = -10 to 28 milliseconds) occurred. PONV occurred in 12 patients and was correlated with morphine equivalent dose (P = .005). CONCLUSIONS: Novel multiple small perioperative methadone doses resulted in safe and lower blood methadone levels, <100 ng/mL, a threshold previously associated with respiratory depression. This methadone dosing in a multimodal regimen resulted in lower blood methadone analgesia concentrations than the historically described minimum analgesic concentrations of methadone from an era before multimodal postoperative analgesia without postoperative respiratory depression and prolonged corrected QT (QTc). Larger studies are needed to further study the safety and efficacy of this methadone dosing strategy.

Involvement of the Peripheral µ-Opioid Receptor in Tramadol-Induced Constipation in Rodents.

Tramadol is a weak opioid that produces analgesic effect via both the µ-opioid receptor (MOR) and non-opioid targets. Constipation is the most common opioid-related side effect in patients with cancer and non-cancer pain. However, the contribution of MOR to tramadol-induced constipation is unclear. Therefore, we used naldemedine, a peripherally acting MOR antagonist, and MOR-knockout mice to investigate the involvement of peripheral MOR in tramadol-induced constipation using a small intestinal transit model. A single dose of tramadol (3-100 mg/kg, per os (p.o.)) inhibited small intestinal transit dose-dependently in rats. Naldemedine (0.01-10 mg/kg, p.o.) blocked the inhibition of small intestinal transit induced by tramadol (30 mg/kg, p.o.) in rats. The transition rate increased dose-dependently over the range of naldemedine 0.01-0.3 mg/kg, and complete recovery was observed at 0.3-10 m/kg. Additionally, tramadol (30 and 100 mg/kg, subcutaneously (s.c.)) inhibited small intestinal transit in wild-type mice but not in MOR-knockout mice. These results suggest that peripheral MOR participates in tramadol-induced constipation.

Effects of different plasma target concentrations of remifentanil on the MACBAR of sevoflurane in children with laparoscopic surgery.

BACKGROUND: To investigate the effects of different plasma target concentrations of remifentanil on the minimum alveolar concentration (MAC) for blocking adrenergic response (BAR) of sevoflurane in children with laparoscopic herniorrhaphy. METHODS: Seventy-five children with 3-7 years old scheduled for laparoscopic herniorrhaphy were randomly divided into group R0, group R1, and group R2 according to different remifentanil plasma target concentration (0, 1, and 2 ngml-1), respectively. The MACBAR of sevoflurane was determined by the up-and-down and sequential method in each group. The concentrations of epinephrine and noradrenaline were also determined at corresponding time points. RESULTS: A total of 52 child patients were used among the anticipated 75 patients. In groups R0, R1, and R2, the MACBAR of sevoflurane was (3.29 ± 0.17) %, (2.12 ± 0.10) % and (1.29 ± 0.11) %, respectively, and a significant difference was found among the three groups (P<0.05). The changes of epinephrine and noradrenaline concentrations in each group before and after insufflation of carbon dioxide pneumoperitoneum showed no significant differences. CONCLUSION: Remifentanil by target-controlled infusion can effectively reduce the MACBAR of sevoflurane during laparoscopic surgery in children. At a similar effect of MACBAR, both the changes of epinephrine and noradrenaline concentrations are not affected by the infusion of different remifentanil target concentrations. TRIAL REGISTRATION: The trial was registered at http://www.chictr.org.cn ( ChiCTR1800019393 , 8, Nov, 2018).

Stereoselective Analysis of Methadone and EDDP in Laboring Women and Neonates in Plasma and Dried Blood Spots and Association with Neonatal Abstinence Syndrome.

OBJECTIVE: This pilot study evaluated the relationship between maternal and neonatal R- and S-methadone and R- and S-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) exposure and the severity of neonatal abstinence syndrome (NAS). The use of dried blood spots (DBS) as an alternative for plasma in assessing methadone and EDDP was also assessed. STUDY DESIGN: Women receiving methadone for medication assisted treatment of opioid use disorder during pregnancy were eligible for recruitment. Plasma and DBS samples were collected from mothers during labor, from cord blood, and from newborns during genetic screen. R-/S-methadone and EDDP were measured by high-performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS). Associations between methadone exposure, neonatal morphine requirements, and severity of NAS were examined. RESULTS: Twenty women and infants completed the study. Maternal methadone dose at delivery was 112 mg/day (range = 60-180 mg/day). Sixteen neonates experienced NAS requiring morphine; three also required phenobarbital. Higher cord blood concentrations of R-methadone, R- and S-EDDP were associated with higher maximum doses of morphine (p < 0.05). CONCLUSION: Maternal methadone and cord blood concentration at delivery are variable and may be potential markers of neonatal abstinence syndrome.

Simultaneous trace-level monitoring of seven opioid analgesic drugs in biological samples by pipette-tip micro solid phase extraction based on PVA-PAA/CNT-CNC composite nanofibers followed by HPLC-UV analysis.

Electrospun poly(vinyl alcohol)-(PVA)-poly(acrylic acid) (PAA)/carbon nanotubes(CNTs)-cellulose nanocrystal (CNC) (PVA-PAA/CNT-CNC) composite nanofibers were prepared and characterized using Fourier transform-infrared spectroscopy and field emission scanning electron microscopy. The resultant composite was used as an effective and novel sorbent for pipette-tip micro-solid phase extraction (PT-µSPE) of seven opioid analgesics (OAs) in biological samples followed by HPLC-UV analysis. Addition of CNT-CNC with the high specific surface area and plenty of OH-functional groups endows the nanofibers with considerable extraction efficiency. Under the optimum conditions, the linearity was obtained in the range 1.5 to 700.0 ng mL-1 for morphine, codeine, oxycodone, and tramadol, and 0.5 to 1000.0 ng mL-1 for nalbuphine, thebaine, and noscapine with coefficient of determination (r2) ≥ 0.9990. Detection limits (LODs) based on S/N = 3 were in the range of 0.15-0.50 ng mL-1. The relative standard deviations (RSDs) of 4.1-5.4% (intra-day, n = 5) and 5.2-6.4% (inter-day, n = 3) for three consecutive days were achieved. Finally, the efficiency of the PT-µSPE-HPLC-UV method was evaluated for the determination of OAs in human plasma and urine samples with good recoveries (87.3 to 97.8%). A: Schematic illustration for the preparation of PVA-PAA/CNT-CNC composite nanofibers. B: Schematic presentation of applying PVA-PAA/CNT-CNC composite nanofibers as the sorbent in pipette-tip micro solid-phase extraction (PT-µSPE) for the preconcentration of seven opioid analgesic drugs in biological samples before HPLC-UV analysis.

Longitudinal Opioid Surveillance Project Involving Toxicologic Analysis of Postmortem Specimens from 9 Counties in Michigan Suggests the Discovery of New High-Intensity Drug Trafficking Areas.

ABSTRACT: Acetyl fentanyl (AF) is a Schedule I fentanyl analog that has been increasingly seen in heroin and fentanyl polydrug toxicity overdoses in Michigan (MI). Drug users are often unaware of the presence of AF in their drugs because it is often sold mixed into or disguised as heroin. High levels of AF in heroin drug products can cause increased incidence of overdose. This article describes data from a longitudinal opioid surveillance program and details 102 decedents in MI who were found to have evidence of heroin in their postmortem blood. A large portion of these decedents were also found to have evidence of fentanyl and AF. Our data further show significant overlap in incidence rates of AF and heroin-related overdose deaths in several MI counties, suggesting that AF is becoming enmeshed in heroin trafficking. Furthermore, we report unprecedented high incidence rates of AF and heroin-related overdose deaths in Calhoun county, and we propose that it is a high-intensity drug trafficking area. Highways US-131 and US-31 are likely used to transport these drugs. More study is needed into the drug trafficking trends in MI to ascertain drug sources and monitor the ever developing and dangerous polydrug heroin combinations.

Xylazine, a Veterinary Tranquilizer, Detected in 42 Accidental Fentanyl Intoxication Deaths.

ABSTRACT: Xylazine is an emerging adulterant with fentanyl in fatal drug intoxications, which has public health, safety, and criminal investigative implications. Xylazine is a nonnarcotic sedative used for analgesia and muscle relaxation exclusively in veterinary medicine. Its chemical structure is similar to clonidine and acts as a central α-2 agonist which may cause bradycardia and transient hypertension followed by hypotension. We report the detection of xylazine in 42 deaths in Connecticut from March to August 2019. Xylazine combined with an opioid or stimulant may affect the toxicity of these drugs. Detection of xylazine may help the forensic pathologist distinguish illicit from prescribed fentanyl, and law enforcement agents track the illicit drugs to a specific drug supplier. Because of its lack of response to naloxone, emergency medicine physicians need to be aware of its potential presence as it may affect therapy.

Lipemia in the Plasma Sample Affects Fentanyl Measurements by Means of HPLC-MS2 after Liquid-Liquid Extraction.

Examination of fentanyl levels is frequently performed in certain scientific evaluations and forensic toxicology. It often involves the collection of very variable blood samples, including lipemic plasma or serum. To date, many works have reported the methods for fentanyl detection, but none of them have provided information about the impact on the assay performance caused by an excessive amount of lipids. This aspect may be, however, very important for highly lipophilic drugs like fentanyl. To address this issue, we developed the liquid chromatography method with mass spectrometry detection and utilized it to investigate the impact of lipids presence in rabbit plasma on the analytical method performance and validation. The validation procedure, conducted for normal plasma and lipemic plasma separately, resulted in good selectivity, sensitivity and linearity. The limits of detection and quantification were comparable between the two matrices, being slightly lower in normal plasma (0.005 and 0.015 µg/L) than in lipemic plasma (0.008 and 0.020 µg/L). Liquid-liquid extraction provided a low matrix effect regardless of the lipid levels in the samples (<10%), but pronounced differences were found in the recovery and accuracy. In the normal plasma, this parameter was stable and high (around 100%), but in the lipemic matrix, much more variable and less efficient results were obtained. Nevertheless, this difference had no impact on repeatability and reproducibility. In the present work, we provided reliable, convenient and sensitive method for fentanyl detection in the normal and lipemic rabbit plasma. However, construction of two separate validation curves was necessary to provide adequate results since the liquid-liquid extraction was utilized. Therefore, special attention should be paid during fentanyl quantification that involves lipemic plasma samples purified by this technique.

High-Performance Liquid Chromatography-Tandem Mass Spectrometry for Buprenorphine Evaluation in Plasma-Application to Pharmacokinetic Studies in Rabbits.

The precise and reliable determination of buprenorphine concentration is fundamental in certain medical or research applications, particularly in pharmacokinetic studies of this opioid. The main challenge is, however, the development of an analytical method that is sensitive enough, as the detected in vivo concentrations often fall in very low ranges. Thus, in this study we aimed at developing a sensitive, repeatable, cost-efficient, and easy HPLC analytical protocol for buprenorphine in rabbit plasma. In order to obtain this, the HPLC-MS2 system was used to elaborate and validate the method for samples purified with liquid-liquid extraction. Fragment ions 468.6→396.2 and 468.6→414.2 were monitored, and the method resulted in a high repeatability and reproducibility and a limit of quantification of 0.25 µg/L with a recovery of 98.7-109.0%. The method was linear in a range of 0.25-2000 µg/L. The suitability of the analytical procedure was tested in rabbits in a pilot pharmacokinetic study, and it was revealed that the method was suitable for comprehensively describing the pharmacokinetic profile after buprenorphine intravenous administration at a dose of 300 µg/kg. Thus, the method suitability for pharmacokinetic application was confirmed by both the good validation results of the method and successful in vivo tests in rabbits.

Efficacy and safety of a monthly buprenorphine depot injection for opioid use disorder: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: RBP-6000, referred to as BUP-XR (extended-release buprenorphine), is a subcutaneously injected, monthly buprenorphine treatment for opioid use disorder. BUP-XR provides sustained buprenorphine plasma concentrations to block drug-liking of abused opioids over the entire monthly dosing period, while controlling withdrawal and craving symptoms. Administration of BUP-XR in a health-care setting also mitigates abuse, misuse, diversion, and unintentional exposure. We aimed to investigate the efficacy of different BUP-XR dosing regimens in participants with opioid use disorder. METHODS: This randomised, double-blind, placebo-controlled, phase 3 trial was done at 36 treatment centres in the USA. Treatment-seeking adults aged 18-65 years who had moderate or severe opioid use disorder (as defined by the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders) entered an open-label run-in phase of up to 2 weeks' treatment with buprenorphine-naloxone sublingual film. Eligible participants were then randomly assigned (4:4:1:1) with an interactive voice/web-response system to receive BUP-XR 300 mg/300 mg (six injections of 300 mg), BUP-XR 300 mg/100 mg (two injections of 300 mg plus four injections of 100 mg), or volume-matched placebo every 28 days, and received weekly individual drug counselling. No supplemental buprenorphine was allowed. The primary efficacy endpoint was participants' percentage abstinence from opioid use, defined as the percentage of each participant's negative urine samples and self-reports of illicit opioid use from week 5 to week 24, analysed in the full analysis set. Safety was assessed in all participants who received at least one dose of BUP-XR or placebo. This study is registered with ClinicalTrials.gov, number NCT02357901. FINDINGS: From Jan 28, 2015, to Nov 12, 2015, 1187 potential participants were screened, 665 entered run-in, and 504 received BUP-XR 300 mg/300 mg (n=201), BUP-XR 300 mg/100 mg (n=203), or placebo (n=100). Mean participants' percentage abstinence was 41·3% (SD 39·7) for BUP-XR 300 mg/300 mg and 42·7% (38·5) for 300 mg/100 mg, compared with 5·0% (17·0) for placebo (p<0·0001 for both BUP-XR regimens). No compensatory non-opioid drug use was observed during BUP-XR treatment. The most common adverse events were headache (17 [8%] participants in the BUP-XR 300 mg/300 mg group vs 19 [9%] participants in the BUP-XR 300 mg/100 mg group vs six [6%] participants in the placebo group), constipation (16 [8%] vs 19 [9%] vs 0), nausea (16 [8%] vs 18 [9%] vs five [5%]), and injection-site pruritis (19 [9%] vs 13 [6%] vs four [4%]). The BUP-XR safety profile was consistent with other buprenorphine products for treatment of opioid use disorder, except for injection-site reactions, which were reported in more than 5% of all participants who received BUP-XR, but were mostly mild and not treatment-limiting. INTERPRETATION: Participants' percentage abstinence was significantly higher in both BUP-XR groups than in the placebo group. Treatment with BUP-XR was also well tolerated. The availability of this monthly formulation, delivered by health-care providers, represents an advance in treatment for opioid use disorder that enhances the benefits of buprenorphine by delivering sustained, optimal exposure, while reducing risks of current buprenorphine products. FUNDING: Indivior.

A genome-wide association study of tramadol metabolism from post-mortem samples.

Phase I tramadol metabolism requires cytochrome p450 family 2, subfamily D, polypeptide 6 (CYP2D6) to form O-desmethyltramadol (M1). CYP2D6 genetic variants may infer metabolizer phenotype; however, drug ADME (absorption, distribution, metabolism, and excretion) and response depend on protein pathway(s), not CYP2D6 alone. There is a paucity of data regarding the contribution of trans-acting proteins to idiosyncratic phenotypes following drug exposure. A genome-wide association study identified five markers (rs79983226/kgp11274252, rs9384825, rs62435418/kgp10370907, rs72732317/kgp3743668, and rs184199168/exm1592932) associated with the conversion of tramadol to M1 (M1:T). These SNPs reside within five genes previously implicated with adverse reactions. Analysis of accompanying toxicological meta-data revealed a significant positive linear relationship between M1:T and degree of sample polypharmacy. Taken together, these data identify candidate loci for potential clinical inferences of phenotype following exposure to tramadol and highlight sample polypharmacy as a possible diagnostic covariate in post-mortem genetic studies.