Morphine-6-glucuronide Research Articles

Pharmacokinetics and thermal anti-nociceptive effects of oral morphine in horses.

Morphine is an effective analgesic in horses, however, IV administration at therapeutic doses has been shown to produce dose-dependent neuroexcitation and unwanted gastrointestinal effects. The analgesic effects of morphine have, at least in part, been attributed to the morphine-6-glucuronide (M6G) metabolite. Oral administration to horses results in comparable M6G concentrations to that achieved following IV administration of a therapeutic dose without the adverse effects. The anti-nociceptive effects have not yet been reported. In the current study the thermal anti-nociceptive effects of single and multiple oral doses of morphine were assessed. Six horses received a single 0.2 mg/kg IV dose of morphine and multiple oral doses of 0.8 mg/kg morphine every 12 h for 4.5 days. Blood samples were collected throughout administration, morphine, and metabolite concentrations determined and pharmacokinetic analysis performed. Drug related behavior and physiologic responses were recorded. Response to noxious stimuli was evaluated by determining thermal threshold latency in response to the application of heat. The maximum concentrations of M6G were higher following oral administration compared to IV and the combined morphine and M6G concentrations exceeded that of IV administration starting at 2 h. Oral administration of 0.8 mg/kg morphine provided and maintained comparable anti-nociception effects to IV morphine with less adverse effects, following single and multiple doses. Morphine was well tolerated following oral administration with less excitation and minimal effects on gastrointestinal borborygmi scores compared to IV administration. Results of the current study warrant further investigation of the anti-nociceptive effects of oral morphine administration to horses.

PBPK-PD model for predicting morphine pharmacokinetics, CNS effects and naloxone antagonism in humans.

Morphine and morphine-6-glucuronide (M6G) produce central nervous system (CNS) effects by activating mu-opioid receptors, while naloxone is used mainly for the reversal of opioid overdose, specifically for the fatal complication of respiratory depression, but also for alleviating opioid-induced side effects. In this study we developed a physiologically-based pharmacokinetic-pharmacodynamic (PBPK-PD) model to simultaneously predict pharmacokinetics and CNS effects (miosis, respiratory depression and analgesia) of morphine as well as antagonistic effects of naloxone against morphine. The pharmacokinetic and pharmacodynamic parameters were obtained from in vitro data, in silico, or animals. Pharmacokinetic and pharmacodynamic simulations were conducted using 39 and 36 clinical reports, respectively. The pharmacokinetics of morphine and M6G following oral or intravenous administration were simulated, and the PBPK-PD model was validated using clinical observations. The Emax model correlated CNS effects with free concentrations of morphine and M6G in brain parenchyma. The predicted CNS effects were compared with observations. Most clinical observations fell within the 5th-95th percentiles of simulations based on 1000 virtual individuals. Most of the simulated area under the concentration-time curve or peak concentrations also fell within 0.5-2-fold of observations. The contribution of morphine to CNS effects following intravenous or oral administration was larger than that of M6G. Pharmacokinetics and antagonistic effects of naloxone on CNS effects were also successfully predicted using the developed PBPK-PD model. In conclusion, the pharmacokinetics and pharmacodynamics of morphine and M6G, antagonistic effects of naloxone against morphine-induced CNS effects may be successfully predicted using the developed PBPK-PD model based on the parameters derived from in vitro, in silico, or animal studies.

Ethno-entomotherapeutic and metabolite profiling of Coridius chinensis (Dallas), a traditional edible insect species of North-East India

Edible insects possess several health enhancing properties and play an important role in human nutrition. Coridius chinensis is an edible insect that is considered food and claimed as traditional medicine. In the present study, nutritional contents, chemical composition, antioxidant, and anti-inflammatory properties of C. chinensis were analyzed. It was found that the insect sample contains 50.46% moisture, 44.65% protein, 4.45% carbohydrate, 39.42% crude fats, 3.53% ash and 576.11 (Kcal/100 g) energy. Our study highlighted the presence of a significant amount of phenol and flavonoids. The C. chinensis hydro-alcoholic extract showed high antioxidant property and anti-inflammatory activity. GCMS analysis identified 61 volatile compounds. LC–MS analysis of hydroalcoholic extract of C. chinensis revealed the presence of compounds such as etodolac glucuronide, morphine 3-glucuronide, ecgonine, ecgonine methyl ester, sufentanil, and palmitoyl ethanololamide. These findings suggest that C. chinensis species can be employed as a valuable food source with excellent therapeutic properties.

Cannabinoid-Induced Inhibition of Morphine Glucuronidation and the Potential for In Vivo Drug-Drug Interactions.

Opioids are commonly prescribed for the treatment of chronic pain. Approximately 50% of adults who are prescribed opioids for pain co-use cannabis with their opioid treatment. Morphine is primarily metabolized by UDP-glucuronosyltransferase (UGT) 2B7 to an inactive metabolite, morphine-3-glucuronide (M3G), and an active metabolite, morphine-6-glucuronide (M6G). Previous studies have shown that major cannabis constituents including Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) inhibit major UGT enzymes. To examine whether cannabinoids or their major metabolites inhibit morphine glucuronidation by UGT2B7, in vitro assays and mechanistic static modeling were performed with these cannabinoids and their major metabolites including 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC), 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (11-COOH-THC), 7-hydroxy-cannabidiol (7-OH-CBD), and 7-carboxy-cannabidiol (7-COOH-CBD). In vitro assays with rUGT-overexpressing microsomes and human liver microsomes showed that THC and CBD and their metabolites inhibited UGT2B7-mediated morphine metabolism, with CBD and THC exhibiting the most potent Ki,u values (0.16 µM and 0.37 µM, respectively). Only 7-COOH-CBD exhibited no inhibitory activity against UGT2B7-mediated morphine metabolism. Static mechanistic modeling predicted an in vivo drug-drug interaction between morphine and THC after inhaled cannabis, and between THC, CBD, and 7-OH-CBD after oral consumption of cannabis. These data suggest that the co-use of these agents may lead to adverse drug events in humans.

Inhibitory Effects of Tricyclic Antidepressants on Human Liver Microsomal Morphine Glucuronidation: Application of IVIVE to Predict Potential Drug-Drug Interactions in Humans.

Tricyclic antidepressants (TCAs) are commonly co-administered with morphine as an adjuvant analgesic. Nevertheless, there remains a lack of information concerning metabolic drug-drug interactions (DDIs) resulting from TCA inhibition on morphine glucuronidation. This study aimed to (i) examine the inhibitory effects of TCAs (viz., amitriptyline, clomipramine, imipramine, and nortriptyline) on human liver microsomal morphine 3- and 6-glucuronidation and (ii) evaluate the potential of DDI in humans by employing in vitro-in vivo extrapolation (IVIVE) approaches. The inhibition parameters for TCA inhibition on morphine glucuronidation were derived from the in vitro system containing 2% BSA. The Ki values were employed to predict the DDI magnitude in vivo by using static and dynamic mechanistic PBPK approaches Results: TCAs moderately inhibited human liver microsomal morphine glucuronidation, with clomipramine exhibiting the most potent inhibition potency. Amitriptyline, clomipramine, imipramine, and nortriptyline competitively inhibited morphine 3- and 6-glucuronide formation with the respective Ki values of 91 ± 7.5 and 82 ± 11 μM, 23 ± 1.3 and 14 ± 0.7 μM, 103 ± 5 and 90 ± 7 μM, and 115 ± 5 and 110 ± 3 μM. Employing the static mechanistic IVIVE, a prediction showed an estimated 20% elevation in the morphine AUC when co-administered with either clomipramine or imipramine, whereas the predicted increase was <5% for amitriptyline or nortriptyline. PBPK modelling predicted an increase of less than 10% in the morphine AUC due to the inhibition of clomipramine and imipramine in both virtual healthy and cirrhotic populations. The results suggest that the likelihood of potential clinical DDIs arising from tricyclic antidepressant inhibition on morphine glucuronidation is low.

Concentrations, pharmacokinetics and selected pharmacodynamics of morphine and its active metabolites following oral administration to horses.

The metabolism and pharmacokinetics of intravenous (i.v.) morphine in the horse have been described; however, administration of therapeutic doses has also been associated with neuroexcitation and adverse gastrointestinal effects. In this study, we hypothesized that oral administration would lead to comparable concentrations of morphine and its presumed active metabolite, morphine 6-glucuronide (M6G) without the adverse effects associated with i.v. administration. Eight horses were administered a single i.v. dose of 0.2mg/kg morphine and oral doses of 0.2, 0.6, and 0.8mg/kg of morphine in a four-way balanced crossover design, with a 2-week washout period between doses. Concentrations of morphine and metabolites were determined, and pharmacokinetic parameters determined. Physiologic and behavioral outcomes including the number of steps taken, changes in heart rate, and gastrointestinal borborygmi were assessed. Oral administration of morphine resulted in higher concentrations of morphine metabolites, including M6G (Cmax : 11.6-37.8ng/mL (0.6mg/kg); 15.8-42.6ng/mL (0.8mg/kg)), compared with i.v. Bioavailability was 36.5%, 27.6% and 28.0% for 0.2, 0.6 and 0.8mg/kg, respectively. Behavioral and physiologic changes were noted in all groups but were less prominent with oral compared with i.v. administration. Results of the current study are encouraging for further study, specifically anti-nociceptive effects of morphine following oral administration.

Morphine in donkeys: Antinociceptive effect and preliminary pharmacokinetics.

Morphine is the prototypical μ-opioid receptor agonist used to provide analgesia in veterinary species. Its effects are well-described in horses but not donkeys. To determine the antinociceptive effects of two doses of morphine in donkeys. To describe preliminary pharmacokinetic parameters of morphine in donkeys. In vivo experiment. Eight adult castrated male donkeys were given intravenous (IV) 0.9% saline, morphine 0.1mg/kg bwt (LDM), or morphine 0.5mg/kg bwt (HDM) in a randomised order with a minimum 1-week washout period. Mechanical nociceptive thresholds (MNTs) were determined by a blinded investigator pre-injection and 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 300, and 360 min post-injection. Venous blood samples were collected pre-injection and 2, 5, 10, 15, 30, 45, 60, 90, and 120 min post-injection. Data were analysed using Friedman's test with Dunn's post hoc test for multiple comparisons. Pharmacokinetic parameters were calculated for the HDM treatment. Baseline MNT was [median (interquartile range)] 8.9 (7.1-10.3) N and did not differ between treatments. Peak MNTs occurred at 60 min for both LDM (16.2N) and HDM (25.0N) treatments. MNTs after HDM treatment were higher than saline (p< 0.04) at 15, 60, 90, 120, 150, 180, 240, and 300 min post-injection. MNTs after LDM treatment were higher than baseline (p< 0.05) at 45 and 60 min post-injection. Terminal half-life for HDM was (mean ± SD) 51.0± 10.7min, the volume of distribution at steady-state 2.07 ± 0.33 L/min and clearance 49.2± 4.16 ml * min/kg using noncompartmental analysis. The concentration of morphine-3-glucuronide (M3G) was higher than morphine-6-glucuronide (M6G) at all sampled time points. Short duration of plasma sampling for pharmacokinetic analysis; lack of objective measure of gastrointestinal function. The HDM treatment provided mechanical antinociception in donkeys with no significant adverse effects.

Highly Sensitive In-Capillary Derivatization and Field Amplified Sample Stacking to Analyze Narcotic Drugs in Human Serum by Capillary Zone Electrophoresis

An in-capillary derivatization (in-CAP-D) integrated with field amplified sample stacking (FASS) has been developed for the determination of morphine (MOR) and its metabolite, morphine-6-glucuronide (MOR-6-G) in human serum using capillary zone electrophoresis (CZE) and fluorescence detection (in-Cap-D-FASS-CZE). Acetonitrile was employed in removing proteins and extracting MOR and MOR-6-G into the clear supernatant containing codeine (COD) as an internal standard (IS). The derivatization was achieved in an in-capillary mode by introducing the acetonitrile-treated samples into a running electrolyte containing an oxidizing agent of potassium ferricyanide, whereas MOR, MOR-6-G and COD were oxidized into dimer derivatives with highly fluorescent intensity. The effectiveness and sensitivity of the in-Cap-D-FASS-CZE method were affected by many parameters, and the following conditions were found to be optimal: 70 m Mdisodium tetraboratedecahydrate (pH, 10.5), 0.30 mM ferrricyanide and a separation voltage of 10 kV. In order to perform the FASS, samples were electrokinetically injected for 20 s at 20 kV into the capillary that was pre-field with a 4 s water plug. Analysis was performed at ambient temperature (22 ± 1 °C). The method’s validation revealed good linearity with respect to peak area ratios of MOR and MOR-6-G with the IS and the corresponding concentrations over the ranges of 1–2000 and 1.2 to 2000 ng/mL, respectively. Following one oral dose of controlled-release MOR sulphate tablet, the validated in-Cap-D-FASS-CZE method successfully enabled the determination of MOR and MOR-6-G in clinical serum samples.

Dissecting the innate immune recognition of morphine and its metabolites by TLR4/MD2: an in silico simulation study.

A toll-like receptor 4/myeloid differentiation factor 2 complex (TLR4/MD2) has been identified as a non-classical opioid receptor capable of recognizing morphine isomers and activating microglia in a non-enantioselective manner. Additionally, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), the major metabolites of morphine, possess similar chemical structures but exhibit distinct effects on TLR4 signaling. However, the specific mechanisms by which morphine isomers and morphine metabolites are recognized by the innate immune receptor TLR4/MD2 are not well understood. Herein, molecular dynamics simulations were performed to dissect the molecular recognition of TLR4/MD2 with morphine isomers, M3G and M6G. Morphine and its (+)-enantiomer, dextro-morphine ((+)-morphine), were found to have comparable binding free energies as well as similar interaction modes when interacting with (TLR4/MD2)2. Binding with morphine and (+)-morphine caused the motion of the F126 loop towards the inside of the MD2 cavity, which stabilizes (TLR4/MD2)2 with similar dimerization interfaces. The binding free energies of M3G and M6G with (TLR4/MD2)2, while lower than those of morphine isomers, were comparable to each other. However, the binding behaviors of M3G and M6G exhibited contrasting patterns when interacting with (TLR4/MD2)2. The glucuronide group of M3G bound to the gating loop of MD2 and formed strong interactions with TLR4*, which stabilizes the active heterotetrameric complex. In contrast, M6G was situated in cavity A of MD2, where the critical interactions between M6G and the residues of TLR4* were lost, resulting in fluctuation of (TLR4/MD2)2 away from the active conformation. These results indicate that the pivotal interactions at the dimerization interface between MD2 and TLR4* in M6G-bound (TLR4/MD2)2 were considerably weaker than those in M3G-bound (TLR4/MD2)2, which partially explains why M6G fails to activate TLR4 signaling. The discoveries from this study will offer valuable insights for the advancement of next-generation TLR4 small molecule modulators based on opioids.

Pharmacokinetics and transplacental transfer of codeine and codeine metabolites from Papaver somniferum L.

Ethnopharmacological relevancePapaveris Pericarpium, which is the dried husk of Papaver somniferum L., has been used as a phytomedicine to relieve cough, diarrhea and pain. The alkaloid codeine contained therein via biotransformation converts to morphine and potentially produces addictive and toxic effects. Due to the healthy concern for a pregnant woman, our hypothesis is that codeine and its metabolites can penetrate the placental barrier to reach the foetus and amniotic fluid, and these processes may be modulated by the transporter. Aim of the studyBecause codeine is also considered a prodrug of morphine, it has a good analgesic effect. It is often used by pregnant women but may expose the foetus to the risk of morphine harm. The aim of this study is to investigate the metabolic rate, distribution and transplacental transfer mechanism of codeine and its metabolites morphine and morphine-3-glucuronide (M3G) in pregnant rats and to assess the risk of medication for pregnant women. Materials and methodsUltrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) combined with a microdialysis system was developed to monitor codeine, morphine and M3G in multiple sites of maternal blood, placenta, foetus and amniotic fluid after codeine administration. A compartmental model was used to calculate the pharmacokinetic parameters of codeine in blood after codeine administration (10 mg/kg, i.v.). The area under the concentration (AUC) ratio of AUCmetabolite/AUCcodeine and AUCtissue/AUCblood was used to represent the metabolic biotransformation ratio and the drug from blood-to-tissue transfer ratio, respectively. ResultsThe pharmacokinetic results demonstrated that codeine fit well with a two-compartment model and went through rapid metabolism to morphine and M3G in pregnant rats after codeine administration (10 mg/kg, i.v.). The biotransformation ratios of AUCmorphine/AUCcodeine, AUCM3G/AUCmorphine and AUCM3G/AUCcodeine were 0.12 ± 0.03, 54.45 ± 20.61 and 6.53 ± 2.47, respectively, after codeine administration (10 mg/kg, i.v.), which suggested that codeine was easily metabolized into M3G through morphine. The tissue distribution results demonstrated that all of the analytes penetrated into the foetus through the placenta; however, the blood-to-tissue transfer ratio (AUCtissue/AUCblood) of morphine and M3G was relatively lower than that of codeine after codeine administration (10 mg/kg, i.v.), which suggested that the blood-placenta barrier blocks the penetration of morphine and M3G into the foetus. Thus, the tissue transfer of morphine in the placenta and foetus was significantly enhanced by treatment with corticosterone, an inhibitor of organic cation transporter (OCT). ConclusionBased on microdialysis coupled to a validated UHPLC–MS/MS system, the pharmacokinetics and metabolic biotransformation of codeine and its metabolites were analyzed and clarified. The potential mechanism of morphine placental transfer was modulated by OCT transporters.

Improving analysis of urine samples from drug-facilitated sexual assault cases

In drug-facilitated sexual assaults (DFSA) the victim is incapacitated by involuntary or voluntary substance consumption. Unfortunately, drug analysis of samples from DFSA is often complicated by late reporting and rapid drug metabolism. Thus, it can be challenging to detect relevant drugs in samples collected more than 24 hours after the assault and sensitive analytical methods are therefore essential. Urine samples provides a longer detection window compared to blood samples. However, many drugs are excreted in urine as conjugated metabolites and sample pretreatment commonly includes an overnight enzymatic hydrolysis under heating conditions. Investigations on the pretreatment conditions and the effects on drug stability provides valuable knowledge in these settings. The aim of this study was to improve enzymatic pretreatment of urine samples and investigate efficiency of a β-glucuronidase/arylsulfatase enzyme using morphine-6-glucuronide as test compound. Additionally, we investigated the stability of 110 drugs and metabolites relevant to DFSA under the optimal pretreatment conditions. To test enzyme efficiency, drug-free urine samples were spiked with morphine-6-glucuronide (M6G) and enzymatically hydrolyzed with β-glucuronidase/arylsulfatase (Helix pomatia, Roche) for 2, 4, 6 and 18 hours at 37 °C. To test drug stability, additional samples spiked with morphine were incubated for 18 hours at 37 °C without enzymatic treatment. After incubation, the enzymatic hydrolysis was stopped by protein precipitation before the extracts were analyzed by UHPLC–MS/MS. To test drug stability for the optimal enzyme incubation time, drug-free urine was collected and spiked with 110 DFSA relevant drugs and metabolites. Samples were either 1) enzymatically hydrolyzed with a β-glucuronidase/arylsulfatase and incubated overnight at 37 °C, 2) incubated overnight at 37 °C without enzymatical hydrolysis or 3) not treated with enzyme or heat. Following overnight incubation, samples were centrifuged twice and diluted with methanol and acetonitrile (50:50) before analysis by UHPLC–MS/MS. Initial results showed that urine samples spiked with morphine and M6G had decreasing concentration of M6G following incubation at 2 h (91% of spiked concentration), 4 h (56%), 6 h (44%), and 18 h (18%). Juxtaposed, morphine concentration increased with incubation at 2 h (19% of theoretical concentration), 4 h (38%), 6 h (47%), and 18 h (92%). This indicated an expected M6G to morphine turnover where the optimal enzyme efficiency was at incubation for 18 h. Results further showed that morphine stability was not affected (recovery: 102%) by heating conditions. In the multi-drug experiment, most drugs were stable under the heating conditions with recoveries above 80%. For some drugs, a decline in concentration was observed after incubation at 37 °C for 18 h, indicating drug instability. For the drug clozapine, the recovery decreased by ¼ while the recovery of the metabolite N-demethylclozapine increased. This demonstrates the importance of including both parent drug and metabolites in the analytical method of urine samples. To prevent this drug instability during pretreatment of urine samples, further experiments will be conducted to examine the use of other enzymes that requires shorter incubation and lower temperatures. The preliminary results showed that the efficiency of a β-glucuronidase/arylsulfatase improved with increasing incubation time. Furthermore, the enzymatical hydrolysis and incubation at 37 °C did not affect the stability of most drugs (75%) relevant to DFSA investigations. This work is financially supported by the Danish Victims Fund (grant number 20-610-0092).

Characterization of the pharmacokinetics, behavioral effects and effects on thermal nociception of morphine 6-glucuronide and morphine 3-glucuronide in horses

ObjectiveTo describe the pharmacokinetics, behavioral and physiologic effects and effects on thermal thresholds of morphine, morphine 6-glucuronide (M6G) and morphine 3-glucuronide (M3G) following administration to horses. Study designRandomized balanced crossover study. AnimalsA total of seven University-owned horses, five mares and two geldings, aged 3–6 years. MethodsHorses were treated with a single intravenous dosage of saline, morphine (0.2 mg kg–1), M6G (0.01 mg kg–1) and M3G (0.03 mg kg–1). Blood was collected prior to (baseline) and at several times post administration. Drug and metabolite concentrations were determined by liquid chromatography–mass spectrometry, and plasma pharmacokinetics were calculated. Behavioral observations and physiologic variables (heart rate, step counts, packed cell volume, total plasma protein and gastrointestinal sounds) were determined at baseline and for up to 6 hours. The effects on thermal nociception were determined and thermal excursion was calculated. ResultsThe volumes of distribution were 4.75–10.5, 0.244–0.295 and 0.215–0.356 L kg–1 for morphine, M6G and M3G, respectively. Systemic clearances were 26.8–39.6, 3.16–3.88 and 1.46–2.13 mL minute−1 kg−1 for morphine, M6G and M3G, respectively. Morphine administration resulted in signs of excitation as evidenced by an increase in step counts and subjective behavioral observations, whereas M6G and M3G, based on the same criteria, appeared to cause sedative-like effects. Significant effects on thermal nociception were observed until 4 hours post morphine administration, 1 hour post M6G administration and at various times post M3G administration. Conclusions and clinical relevanceResults of this study provide additional information regarding the use of morphine in horses. Less locomotor excitation and gastrointestinal adverse effects, compared with morphine, coupled with favorable effects on thermal nociception are encouraging for further study of the pharmacodynamics of both M6G and M3G in horses.

PHARMACOGENETIC ASPECTS OF THE USE OF PERIOPERATIVE DRUGS IN PEDIATRICS. Review

Relevance. It is known that in children the frequency of perioperative critical events due to the introduction of drugs is more than 5%. For example fentanyl, which is used as an adjunct to surgical anesthesia, is a major factor in increasing the number of deaths from opioid overdoses. Among the areas of reducing the frequency of severe adverse reactions to perioperative drugs - taking into account the pharmacogenetic variations of the patient.&#x0D; Objective is to consider current data on pharmacogenetic aspects of pharmacokinetics and pharmacodynamics of perioperative drugs.&#x0D; Methods. Analysis of the data presented in PubMed by keywords "pharmacogenetics", "general anesthetics", "analgesics", "muscle relaxants", "children". Search depth – 7 years (2014-2020), with a retrospective deepening of some positions until 2002.&#x0D; Results. The pharmacogenetic aspects of the pharmacokinetics of perioperative drugs are related to the genes of the enzymes that metabolize them and their transporters. Current data on the prevalence of polymorphic alleles of CYP2C9 genes (provides metabolism of nonsteroidal anti-inflammatory and anticonvulsant drugs) and CYP2D6 (metabolizes opioids, antidepressants, antiemetics) in Europe and, in particular, in Ukraine were presented. Thus, the inactive allele CYP2C19 * 2 was found in 13%, while the allele of increased activity CYP2C19 * 17 - in 25% of the population of Ukraine; allele with lost CYP2D6 function (CYP2D6 * 4) - in 18.6% of Ukrainians. Homozygotes with CYP2C9 * 3 polymorphism metabolize nonsteroidal anti-inflammatory drugs much more slowly than wild-type carriers, which may lead to their accumulation and side effects. The analgesic effect of codeine occurs only after it is metabolized in the liver by CYP2D6 to morphine. Respiratory depression, apnea and death may occur in patients with excessive metabolic rate even after a single dose of codeine; however, was noted the ineffectiveness of ondansetron due to a decrease in its concentration in the blood in thesepatients. Concomitant use of midazolam and fentanyl may prolong the effect of fentanyl by competing metabolism of midazolam by the hepatic enzyme CYP3A4, especially in patients with low metabolism. Plasma butyrylcholinesterase deficiency reduces succinylcholine inactivation in 1 in 1,500 people. Changing the genotype of uridine diphosphate glycosyltransferase causes increased glucuronidation of morphine, which may lead to a decrease in its effectiveness. As an example of pharmacogenetic changes in pharmacodynamics can be considered malignant hyperthermia, which occurs due to exposure to volatile anesthetics and depolarizing muscle relaxants in mutations in the RYR1 gene. Carriers of the minor allele (G) of the 5HT2A rs6313 gene require less propofol and 40% less time to start induction of anesthesia.&#x0D; Conclusions. The efficacy and safety of perioperative drugs are largely related to the pharmacogenetic aspects of their pharmacokinetics, especially mutations in genes of enzymes of the metabolism. Mutations in the genes of volatile anesthetic receptors and depolarizing muscle relaxants when their used cause a risk of malignant hyperthermia. The application of pharmacogenetics is the need to titrate drugs that have significant variability of action depending on the genotype. It is advisable to avoid the use of drugs with a high risk of pharmacogenetic reactions, if other alternative drugs are available.

Pharmacokinetics, adverse effects and effects on thermal nociception following administration of three doses of codeine to horses

BackgroundIn humans, codeine is a commonly prescribed analgesic that produces its therapeutic effect largely through metabolism to morphine. In some species, analgesic effects of morphine have also been attributed to the morphine-6-glucuronide (M6G) metabolite. Although an effective analgesic, administration of morphine to horses produces dose-dependent neuroexcitation at therapeutic doses. Oral administration of codeine at a dose of 0.6 mg/kg has been shown to generate morphine and M6G concentrations comparable to that observed following administration of clinically effective doses of morphine, without the concomitant adverse effects observed with morphine administration. Based on these results, it was hypothesized that codeine administration would provide effective analgesia with decreased adverse excitatory effects compared to morphine. Seven horses received a single oral dose of saline or 0.3, 0.6 or 1.2 mg/kg codeine or 0.2 mg/kg morphine IV (positive control) in a randomized balanced 5-way cross-over design. Blood samples were collected up to 72 hours post administration, codeine, codeine 6-glucuronide, norcodeine morphine, morphine 3-glucuronide and M6G concentrations determined by liquid chromatography- mass spectrometry and pharmacokinetic analysis performed. Pre- and post-drug related behavior, locomotor activity, heart rate and gastrointestinal borborygmi were recorded. Response to noxious stimuli was evaluated by determining thermal threshold latency.ResultsMorphine concentrations were highest in the morphine dose group at all times post administration, however, M6G concentrations were significantly higher in all the codeine dose groups compared to the morphine group starting at 1 hour post drug administration and up to 72-hours in the 1.2 mg/kg group. With the exception of one horse that exhibited signs of colic following administration of 0.3 and 0.6 mg/kg, codeine administration was well tolerated. Morphine administration, led to signs of agitation, tremors and excitation. There was not a significant effect on thermal nociception in any of the dose groups studied.ConclusionsThe current study describes the metabolic profile and pharmacokinetics of codeine in horses and provides information that can be utilized in the design of future studies to understand the anti-nociceptive and analgesic effects of opioids in this species with the goal of promoting judicious and safe use of this important class of drugs.

Simultaneous detection of a panel of nine sedatives and metabolites in plasma from critically ill pediatric patients via UPLC-MS/MS

Sedative use can result in adverse drug reactions. Intensive care unit patients are especially at risk and pharmacokinetic modeling of drug concentrations is an approach to develop precision dosing strategies. However, limited blood sampling availability in critically ill children and need for multiple assays to quantify a variety of commonly used sedatives creates logistical challenges. The goal of this project was to develop a sensitive and selective assay for the simultaneous quantification of a panel of sedatives comprised of midazolam (MDZ), alpha hydroxymidazolam (1- OH MDZ), dexmedetomidine (DEX), morphine (MOR), morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G), fentanyl (FEN), norfentanyl (NF), and hydromorphone (HM) in small volume pediatric plasma samples. A sensitive and efficient ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method was developed following FDA guidance for bioanalytical validation. Minimal sample preparation consisting of simple protein precipitation extraction using acetonitrile with internal standards was utilized. Analyte separation was achieved using a gradient mixture of (A: 0.15% formic acid in water and B: Acetonitrile) and a Waters Acquity C18, 1.7 µm (2.1 × 100 mm) column. Assays were linear over the clinical concentration ranges: MDZ, MOR, HM: 0.5–125 ng/mL; 1-OH MDZ, M3G, M6G: 5–500 ng/mL; and DEX, FEN, NF: 0.05–7.5 ng/mL (R2 > 0.99 for all). Assay run time was 10 min and required only 100 μL of plasma. Initial testing of samples from pediatric patients demonstrates adequacy of assay to measure sedatives and metabolites at clinical concentrations confidently in low volumes of plasma. This novel highly-sensitive and specific method to measure a total of nine different analytes (five sedatives, four metabolites) simultaneously enables comprehensive analysis of a panel of sedatives in small volumes such as in pediatric ICU patients.

Morphine-3-Glucuronide, Physiology and Behavior.

Morphine remains the gold standard painkiller available to date to relieve severe pain. Morphine metabolism leads to the production of two predominant metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). This metabolism involves uridine 5′-diphospho-glucuronosyltransferases (UGTs), which catalyze the addition of a glucuronide moiety onto the C3 or C6 position of morphine. Interestingly, M3G and M6G have been shown to be biologically active. On the one hand, M6G produces potent analgesia in rodents and humans. On the other hand, M3G provokes a state of strong excitation in rodents, characterized by thermal hyperalgesia and tactile allodynia. Its coadministration with morphine or M6G also reduces the resulting analgesia. Although these behavioral effects show quite consistency in rodents, M3G effects are much more debated in humans and the identity of the receptor(s) on which M3G acts remains unclear. Indeed, M3G has little affinity for mu opioid receptor (MOR) (on which morphine binds) and its effects are retained in the presence of naloxone or naltrexone, two non-selective MOR antagonists. Paradoxically, MOR seems to be essential to M3G effects. In contrast, several studies proposed that TLR4 could mediate M3G effects since this receptor also appears to be essential to M3G-induced hyperalgesia. This review summarizes M3G’s behavioral effects and potential targets in the central nervous system, as well as the mechanisms by which it might oppose analgesia.

Inhibition of Morphine Metabolism by Major Cannabinoids and their Metabolites

Opioids including morphine are mu‐opioid receptor (MOR) agonists that suppress excitatory neurotransmitter release, hyperpolarize neuronal cells, and decrease overall excitability, resulting in the desired analgesic effect. As a result of their over‐prescription, the still‐growing opioid epidemic has devastated many communities, with many individuals often using them in combination with other drugs including cannabis. Morphine is primarily metabolized by the phase II enzyme UDP‐glucuronosyltransferase (UGT) 2B7 to an inactive metabolite, morphine‐3‐glucuronide (M3G), and an active metabolite, morphine‐6‐glucuronide (M6G), both of which are extensively excreted into the urine. Previous studies in our lab have shown that major cannabis constituents including Δ9‐tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol (CBN) inhibit several major UGT enzymes. To examine whether cannabinoids or their major metabolites inhibit morphine glucuronidation by UGT2B7, screening assays were performed in pooled human liver microsomes (HLM) with the major cannabinoids and THC metabolites, 11‐hydroxy‐Δ9‐tetrahydrocannabinol (11‐OH‐THC), 11‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol (11‐COOH‐THC), and 11‐nor‐Δ9‐tetrahydrocannabinol‐carboxylic acid glucuronide (THC‐COO‐Gluc). IC50 values were then determined for those cannabinoids that exhibited at least 50% inhibition at 100 µM final concentration. THC, 11‐OH‐THC, THC‐COO‐Gluc, and CBD all exhibited greater than 50% inhibition of both M3G and M6G formation at either 10 or 100 µM. The IC50 values for THC, 11‐OH‐THC, THC‐COO‐Gluc, and CBD against M3G formation were determined to be 27 ± 9.97 µM, 5.97 ± 2.31 µM, 15.58 ± 12.28 µM, and 15.66 ± 19.98 µM, respectively. The IC50 values for THC, 11‐OH‐THC, THC‐COO‐Gluc, and CBD against M6G formation were 14.49 ± 4.03 µM, 6.26 ± 0.76 µM, 13.22 ± 5.28 µM, and 8.12 ± 9.64 µM, respectively. To confirm results from these inhibition screenings, M3G and M6G formation were further examined using microsomal fractions from HEK293 cells overexpressing recombinant UGT2B7. THC, 11‐OH‐THC, THC‐COO‐Gluc, and CBD all exhibited &gt;50% inhibition of both M3G and M6G formation at either 10 or 100 µM in the recombinant enzyme system. These data suggest that several cannabinoids and their metabolites inhibit morphine metabolism, and that the co‐use of these agents may lead to adverse drug events in humans.

Central metabolism as a potential origin of sex differences in morphine antinociception but not induction of antinociceptive tolerance in mice.

In rodents, morphine antinociception is influenced by sex. However, conflicting results have been reported regarding the interaction between sex and morphine antinociceptive tolerance. Morphine is metabolised in the liver and brain into morphine-3-glucuronide (M3G). Sex differences in morphine metabolism and differential metabolic adaptations during tolerance development might contribute to behavioural discrepancies. This article investigates the differences in peripheral and central morphine metabolism after acute and chronic morphine treatment in male and female mice. Sex differences in morphine antinociception and tolerance were assessed using the tail-immersion test. After acute and chronic morphine treatment, morphine and M3G metabolic kinetics in the blood were evaluated using LC-MS/MS. They were also quantified in several CNS regions. Finally, the blood-brain barrier (BBB) permeability of M3G was assessed in male and female mice. This study demonstrated that female mice showed weaker morphine antinociception and faster induction of tolerance than males. Additionally, female mice showed higher levels of M3G in the blood and in several pain-related CNS regions than male mice, whereas lower levels of morphine were observed in these regions. M3G brain/blood ratios after injection of M3G indicated no sex differences in M3G BBB permeability, and these ratios were lower than those obtained after injection of morphine. These differences are attributable mainly to morphine central metabolism, which differed between males and females in pain-related CNS regions, consistent with weaker morphine antinociceptive effects in females. However, the role of morphine metabolism in antinociceptive tolerance seemed limited. This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

Inhibitory effects of non-steroidal anti-inflammatory drugs on human liver microsomal morphine glucuronidation: Implications for drug-drug interaction liability

The inhibitory effects of fifteen NSAIDs from six structurally distinct classes on human liver microsomal morphine glucuronidation were investigated. Ki values of selected NSAIDs were generated and employed to assess DDI liability in vivo. Potent inhibition was observed for mefenamic acid and tolfenamic acid; respective IC50 values for morphine 3- and 6-glucuronidation were 9.2 and 13.5 μM, and 5.3 and 8.3 μM. Diclofenac and celecoxib showed moderate inhibition with IC50 values of 78 and 52 μM, and 83 and 214 μM, respectively. Estimated IC50 values for the other NSAIDs screened were >100 μM. Mefenamic acid, diclofenac, and S-naproxen competitively inhibited morphine 3- and 6-glucuronidation, with the Ki values of 11 and 12 μM, 110 and 76 μM, and 319 and 650 μM, respectively. Using the static mechanistic IVIVE approach, an approximate 40% increase in the AUC of morphine was predicted when co-administered with mefenamic acid, whereas the increase was <10% with diclofenac and S-naproxen. PBPK modeling predicted <15% increases in the morphine AUC from diclofenac and S-naproxen inhibition in virtual healthy and cirrhotic subjects. The data suggest that potential clinically significant DDIs arising from NSAID inhibition of morphine glucuronidation is unlikely, with the possible exception of some fenamates.

Dexamethasone Does not Compensate for Local Anesthetic Cytotoxic Effects on Tenocytes: Morphine or Morphine Plus Dexamethasone May Be a Safe Alternative

PurposeThe purposes of this in vitro study were to investigate whether the addition of dexamethasone can compensate for any cytotoxic effects of the amide-type local anesthetics (LA) bupivacaine and ropivacaine and whether morphine and morphine-6-glucuronide (M6G) may be a safe alternative for peritendinous application.MethodsBiopsies of human biceps tendons (n = 6) were dissected and cultivated. Cells were characterized by the expression for tenocyte markers, collagen I, biglycan, tenascin C, scleraxis, and RUNX via reverse transcriptase-polymerase chain reaction and immunohistochemistry. Tenocytes were incubated with bupivacaine, ropivacaine, morphine, M6G, or a saline control with and without addition of dexamethasone for 15, 60, or 240 min. Cell viability was determined by quantifying the presence of adenosine-triphosphate.ResultsSignificant time-dependent cytotoxic effects were observed for LA after all exposure times. After 15, 60, and 240 minutes, cell viability decreased to 81.1%, 49.4% and 0% (P < .001) for bupivacaine and to 81.4%, 69.6%, and 9.3% (P < .001) for ropivacaine compared to saline control. Dexamethasone did not compensate for these cytotoxic effects. Cell viability was not affected after 15, 60-min exposures to morphine and M6G but decreased significantly (P < .001) after 240 minutes compared to saline control. However, in combination with dexamethasone, tenocyte viability was significantly increased at all times for morphine (P < .01) and at 15 and 60 minutes for M6G (P < .01).ConclusionsThe results showed that amide-type LA have a time-dependent cytotoxic effect on human tenocytes in vitro, which could not be compensated for by dexamethasone, whereas morphine and M6G had no cytotoxic effects on tenocytes after 15 and 60 minutes. The addition of dexamethasone to morphine and M6G had a positive effect on viability, which increased significantly compared to the opioids.Clinical RelevanceIt is known that amide-type local anesthetics used for local joint analgesia have chondrotoxic side-effects. The combined application of morphine and dexamethasone may be a safe alternative.