Lucie Chevillard

Interaction of drugs of abuse and maintenance treatments with human P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2)

Drug interaction with P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) may influence its tissue disposition including blood-brain barrier transport and result in potent drug-drug interactions. The limited data obtained using in-vitro models indicate that methadone, buprenorphine, and cannabinoids may interact with human P-gp; but almost nothing is known about drugs of abuse and BCRP. We used in vitro P-gp and BCRP inhibition flow cytometric assays with hMDR1- and hBCRP-transfected HEK293 cells to test 14 compounds or metabolites frequently involved in addiction, including buprenorphine, norbuprenorphine, methadone, ibogaine, cocaine, cocaethylene, amphetamine, N-methyl-3,4-methylenedioxyamphetamine, 3,4-methylenedioxyamphetamine, nicotine, ketamine, Delta9-tetrahydrocannabinol (THC), naloxone, and morphine. Drugs that in vitro inhibited P-gp or BCRP were tested in hMDR1- and hBCRP-MDCKII bidirectional transport studies. Human P-gp was significantly inhibited in a concentration-dependent manner by norbuprenorphine>buprenorphine>methadone>ibogaine and THC. Similarly, BCRP was inhibited by buprenorphine>norbuprenorphine>ibogaine and THC. None of the other tested compounds inhibited either transporter, even at high concentration (100 microm). Norbuprenorphine (transport efflux ratio approoximately 11) and methadone (transport efflux ratio approoximately 1.9) transport was P-gp-mediated; however, with no significant stereo-selectivity regarding methadone enantiomers. BCRP did not transport any of the tested compounds. However, the clinical significance of the interaction of norbuprenorphine with P-gp remains to be evaluated.

Characteristics and comparative severity of respiratory response to toxic doses of fentanyl, methadone, morphine, and buprenorphine in rats

Opioids are known to induce respiratory depression. We aimed to characterize in rats the effects of four opioids on arterial blood gases and plethysmography after intraperitoneal administration at 80% of their LD(50) in order to identify opioid molecule-specific patterns and classify response severity. Opioid-receptor (OR) antagonists, including intravenous 10 mg kg(-1)-naloxonazine at 5 min [mu-OR antagonist], subcutaneous 30 mg kg(-1)-naloxonazine at 24 h [mu1-OR antagonist], subcutaneous 3 mg kg(-1)-naltrindole at 45 min [delta-OR antagonist], and subcutaneous 5 mg kg(-1)-Nor-binaltorphimine at 6 h [kappa-OR antagonist] were pre-administered to test the role of each OR. Methadone, morphine, and fentanyl significantly decreased PaO(2) (P<0.001) and increased PaCO(2) (P<0.05), while buprenorphine only decreased PaO(2) (P<0.05). While all opioids significantly increased inspiratory time (T(I), P<0.001), methadone and fentanyl also increased expiratory time (T(E), P<0.05). Intravenous 10 mg kg(-1)-naloxonazine at 5 min completely reversed opioid-related effects on PaO(2) (P<0.05), PaCO(2) (P<0.001), T(I) (P<0.05), and T(E) (P<0.01) except in buprenorphine. Subcutaneous 30 mg kg(-1)-naloxonazine at 24 h completely reversed effects on PaCO(2) (P<0.01) and T(E) (P<0.001), partially reversed effects on T(I) (P<0.001), and did not reverse effects on PaO(2). Naltrindole reversed methadone-induced T(E) increases (P<0.01) but worsened fentanyls effect on PaCO(2) (P<0.05) and T(I) (P<0.05). Nor-binaltorphimine reversed morphine- and buprenorphine-induced T(I) increases (P<0.001) but worsened methadones effect on PaO(2) (P<0.05) and morphine (P<0.001) and buprenorphines (P<0.01) effects on pH. In conclusion, opioid-related respiratory patterns are not uniform. Opioid-induced hypoxemia as well as increases in T(I) and T(E) are caused by mu-OR, while delta and kappa-OR roles appear limited, depending on the specific opioid. Regarding severity of opioid-induced respiratory effects at 80% of their LD(50), all drugs increased T(I). Methadone and fentanyl induced hypoxemia, hypercapnia, and T(E) increases, morphine caused both hypoxemia and hypercapnia while buprenorphine caused only hypoxemia.

Mechanisms of respiratory insufficiency induced by methadone overdose in rats.

Methadone may cause respiratory depression. We aimed to understand methadone‐related effects on ventilation as well as each opioid‐receptor (OR) role. We studied the respiratory effects of intraperitoneal methadone at 1.5, 5, and 15 mg/kg (corresponding to 80% of the lethal dose‐50%) in rats using arterial blood gases and plethysmography. OR antagonists, including intravenous 10 mg/kg‐naloxonazine at 5 minutes (mu‐OR antagonist), subcutaneous 30 mg/kg‐naloxonazine at 24 hours (mu1‐OR antagonist), 3 mg/kg‐naltrindole at 45 minutes (delta‐OR antagonist) and 5 mg/kg‐Nor‐binaltorphimine at 6 hours (kappa‐OR antagonist) were pre‐administered. Plasma concentrations of methadone enantiomers were measured using high‐performance liquid chromatography coupled to mass‐spectrometry. Methadone dose‐dependent inspiratory time (TI) increase tended to be linear. Respiratory depression was observed only at 15 mg/kg and characterized by an increase in expiratory time (TE) resulting in hypoxemia and respiratory acidosis. Intravenous naloxonazine completely reversed all methadone‐related effects on ventilation, while subcutaneous naloxonazine reduced its effects on pH (P < 0.05), PaCO2 (P < 0.01) and TE (P < 0.001) but only partially on TI (P < 0.001). Naltrindole reduced methadone‐related effects on TE (P < 0.001). Nor‐binaltorphimine increased methadone‐related effects on pH and PaO2 (P < 0.05) Respiratory effects as a function of plasma R‐methadone concentrations showed a decrease in PaO2 (EC50: 1.14 µg/ml) at lower concentrations than those necessary for PaCO2 increase (EC50: 3.35 µg/ml). Similarly, increased TI (EC50: 0.501 µg/ml) was obtained at lower concentrations than those for TE (EC50: 4.83 µg/ml). Methadone‐induced hypoxemia is caused by mu‐ORs and modulated by kappa‐ORs. Additionally, methadone‐induced increase in TE is caused by mu1‐ and delta‐opioid receptors while increase in TI is caused by mu‐ORs.

Bifunctional Peptide-Based Opioid Agonist–Nociceptin Antagonist Ligands for Dual Treatment of Acute and Neuropathic Pain

Herein, the opioid pharmacophore H-Dmt-d-Arg-Aba-β-Ala-NH2 (7) was linked to peptide ligands for the nociceptin receptor. Combination of 7 and NOP ligands (e.g., H-Arg-Tyr-Tyr-Arg-Ile-Lys-NH2) led to binding affinities in the low nanomolar domain. In vitro, the hybrids behaved as agonists at the opioid receptors and antagonists at the nociceptin receptor. Intravenous administration of hybrid 13a (H-Dmt-d-Arg-Aba-β-Ala-Arg-Tyr-Tyr-Arg-Ile-Lys-NH2) to mice resulted in potent and long lasting antinociception in the tail-flick test, indicating that 13a was able to permeate the BBB. This was further supported by a cell-based BBB model. All hybrids alleviated allodynia and hyperalgesia in neuropathic pain models. Especially with respect to hyperalgesia, they showed to be more effective than the parent compounds. Hybrid 13a did not result in significant respiratory depression, in contrast to an equipotent analgesic dose of morphine. These hybrids hence represent a promising avenue toward analgesics for the dual treatment of acute and neuropathic pain.

Study of Blood and Brain Lithium Pharmacokinetics in the Rat According to Three Different Modalities of Poisoning

Lithium-induced neurotoxicity may be life threatening. Three patterns have been described, including acute, acute-on-chronic, and chronic poisoning, with unexplained discrepancies in the relationship between clinical features and plasma lithium concentrations. Our objective was to investigate differences in plasma, erythrocyte, cerebrospinal fluid, and brain lithium pharmacokinetics using a multicompartmental approach in rat models mimicking the three human intoxication patterns. We developed acute (intraperitoneal administration of 185 mg/kg Li₂CO₃ in naive rats), acute-on-chronic (intraperitoneal administration of 185 mg/kg Li₂CO₃ in rats receiving 800 mg/l Li₂CO₃ in water during 28 days), and chronic poisoning models (intraperitoneal administration of 74 mg/kg Li₂CO₃ during 5 days in rats with 15 mg/kg K₂Cr₂O₇-induced renal failure). Delayed absorption (4.03 vs 0.31 h), increased plasma elimination (0.65 vs 0.37 l/kg/h) and shorter half-life (1.75 vs 2.68 h) were observed in acute-on-chronically compared with acutely poisoned rats. Erythrocyte and cerebrospinal fluid kinetics paralleled plasma kinetics in both models. Brain lithium distribution was rapid (as early as 15 min), inhomogeneous and with delayed elimination (over 78 h). However, brain lithium accumulation was more marked in acute-on-chronically than acutely poisoned rats [area-under-the-curve of brain concentrations (379 ± 41 vs 295 ± 26, P < .05) and brain-to-plasma ratio (45 ± 10 vs 8 ± 2, P < .0001) at 54 h]. Moreover, brain lithium distribution was increased in chronically compared with acute-on-chronically poisoned rats (brain-to-plasma ratio: 9 ± 1 vs 3 ± 0, P < .01). In conclusion, prolonged rat exposure results in brain lithium accumulation, which is more marked in the presence of renal failure. Our data suggest that differences in plasma and brain kinetics may at least partially explain the observed variability between human intoxication patterns.

Respiratory effects of buprenorphine/naloxone alone and in combination with diazepam in naive and tolerant rats

Respiratory depression has been attributed to buprenorphine (BUP) misuse or combination with benzodiazepines. BUP/naloxone (NLX) has been marketed as maintenance treatment, aiming at preventing opiate addicts from self-injecting crushed pills. However, to date, BUP/NLX benefits in comparison to BUP alone remain debated. We investigated the plethysmography effects of BUP/NLX in comparison to BUP/solvent administered by intravenous route in naive and BUP-tolerant Sprague-Dawley rats, and in combination with diazepam (DZP) or its solvent. In naive rats, BUP/NLX in comparison to BUP significantly increased respiratory frequency (f, P<0.05) without altering minute volume (VE). In combination to DZP, BUP/NLX significantly increased expiratory time (P<0.01) and decreased f (P<0.01), tidal volume (VT, P<0.001), and VE (P<0.001) while BUP only decreased VT (P<0.5). In BUP-tolerant rats, no significant differences in respiratory effects were observed between BUP/NLX and BUP. In contrast, in combination to DZP, BUP/NLX did not significantly alter the plethysmography parameters, while BUP increased inspiratory time (P<0.001) and decreased f (P<0.01) and VE (P<0.001). In conclusion, differences in respiratory effects between BUP/NLX and BUP are only significant in combination with DZP, with increased depression in naive rats but reduced depression in BUP-tolerant rats. However, BUP/NLX benefits in humans remain to be determined.

Mechanisms of tramadol-related neurotoxicity in the rat: Does diazepam/tramadol combination play a worsening role in overdose? ☆

Poisoning with opioid analgesics including tramadol represents a challenge. Tramadol may induce respiratory depression, seizures and serotonin syndrome, possibly worsened when in combination to benzodiazepines. Our objectives were to investigate tramadol-related neurotoxicity, consequences of diazepam/tramadol combination, and mechanisms of drug-drug interactions in rats. Median lethal-doses were determined using Dixon-Bruces up-and-down method. Sedation, seizures, electroencephalography and plethysmography parameters were studied. Concentrations of tramadol and its metabolites were measured using liquid-chromatography-high-resolution-mass-spectrometry. Plasma, platelet and brain monoamines were measured using liquid-chromatography coupled to fluorimetry. Median lethal-doses of tramadol and diazepam/tramadol combination did not significantly differ, although time-to-death was longer with combination (P=0.04). Tramadol induced dose-dependent sedation (P<0.05), early-onset seizures (P<0.001) and increase in inspiratory (P<0.01) and expiratory times (P<0.05). The diazepam/tramadol combination abolished seizures but significantly enhanced sedation (P<0.01) and respiratory depression (P<0.05) by reducing tidal volume (P<0.05) in addition to tramadol-related increase in respiratory times, suggesting a pharmacodynamic mechanism of interaction. Plasma M1 and M5 metabolites were mildly increased, contributing additionally to tramadol-related respiratory depression. Tramadol-induced early-onset increase in brain concentrations of serotonin and norepinephrine was not significantly altered by the diazepam/tramadol combination. Interestingly neither pretreatment with cyproheptadine (a serotonin-receptor antagonist) nor a benserazide/5-hydroxytryptophane combination (enhancing brain serotonin) reduced tramadol-induced seizures. Our study shows that diazepam/tramadol combination does not worsen tramadol-induced fatality risk but alters its toxicity pattern with enhanced respiratory depression but abolished seizures. Drug-drug interaction is mainly pharmacodynamic but increased plasma M1 and M5 metabolites may also contribute to enhancing respiratory depression. Tramadol-induced seizures are independent of brain serotonin.

Bifunctional peptide-based opioid agonist/nociceptin antagonist ligand for dual treatment of nociceptive and neuropathic pain

Abstract Drugs able to treat both nociceptive and neuropathic pain effectively without major side effects are lacking. We developed a bifunctional peptide-based hybrid (KGNOP1) that structurally combines a mu-opioid receptor agonist (KGOP1) with antinociceptive activity and a weak nociceptin receptor antagonist (KGNOP3) with anti-neuropathic pain activity. We investigated KGNOP1-related behavioral effects after intravenous administration in rats by assessing thermal nociception, cold hyperalgesia in a model of neuropathic pain induced by chronic constriction injury of the sciatic nerve, and plethysmography parameters including inspiratory time (TI) and minute ventilation (VM) in comparison to the well-known opioid analgesics, tramadol and morphine. Time-course and dose-dependent effects were investigated for all behavioral parameters to determine the effective doses 50% (ED50). Pain-related effects on cold hyperalgesia were markedly increased by KGNOP1 as compared to KGNOP3 and tramadol (ED50: 0.0004, 0.32, and 12.1 &mgr;mol/kg, respectively), whereas effects on thermal nociception were significantly higher with KGNOP1 as compared to morphine (ED50: 0.41 and 14.7 &mgr;mol/kg, respectively). KGNOP1 and KGOP1 produced a larger increase in TI and deleterious decrease in VM in comparison to morphine and tramadol (ED50(TI): 0.63, 0.52, 12.2, and 50.9 &mgr;mol/kg; ED50(VM): 0.57, 0.66, 10.6, and 50.0 &mgr;mol/kg, respectively). Interestingly, the calculated ratios of anti-neuropathic pain/antinociceptive to respiratory effects revealed that KGNOP1 was safer than tramadol (ED50 ratio: 5.44 × 10−3 vs 0.24) and morphine (ED50 ratio: 0.72 vs 1.39). We conclude that KGNOP1 is able to treat both experimental neuropathic and nociceptive pain, more efficiently and safely than tramadol and morphine, respectively, and thus should be a candidate for future clinical developments.

Lithium-related neurotoxicity despite serum concentrations in the therapeutic range: risk factors and diagnosis.

An 18-year old female with mania developed confusion, trembling extremities, slurred speech, increased muscle tension, and hyperactive tendon reflexes 20 days after initiating treatment with routine dosages of lithium bicarbonate. When admitted to the hospital due to her acute neurological condition, her serum lithium concentration was in the therapeutic range (0.57 mmol/L). Most of her symptoms spontaneously reversed one week after stopping the lithium. Since its approval by the Food and Drug Administration in 1970 as treatment for bipolar disorders, several studies have addressed lithium-related neurotoxicity and the related risk factors; these studies all emphasize the relatively narrow therapeutic index of lithium. With the exception of intentional ingestion of large doses of lithium as an act of self-harm (resulting in ‘acute intoxication’ in untreated individuals or ‘acute-onchronic intoxication’ in currently treated individuals), toxicity during prolonged treatment with lithium (‘chronic intoxication’) usually results from progressive lithium accumulation due to renal dysfunction, underlying diseases, low sodium intake, and drug– drug interactions such as loop diuretics, angiotensinconverting enzyme inhibitors, or non-steroidal antiinflammatory drugs. [2]

Development, validation and clinical application of a LC-MS/MS method for the simultaneous quantification of hydroxychloroquine and its active metabolites in human whole blood

A rapid, sensitive and specific method using liquid chromatography coupled to tandem mass spectrometry was developed for the simultaneous quantification of hydroxychloroquine (HCQ) and its three major metabolites in human whole blood. The assay, using a sample volume of 100μL, was linear in a dynamic 25-2000ng/mL range (R(2)>0.99) for all four compounds and suitable for the determination of elevated HCQ concentrations up to 20,000ng/mL, after appropriate sample dilution. Inter- and intra-assay precisions were <18.2% and accuracies were between 84% and 113% for any analyte. No matrix effects were observed. The assay was successfully applied to a blood sample obtained from one poisoned patient following a massive HCQ self-ingestion resulting in an estimated concentration of 19,500ng/mL on hospital admission. In this patient, HCQ metabolites were identified and quantified at 1123, 465 and 91ng/mL for monodesethylhydroxychloroquine, desethylchloroquine and bisdesethylchloroquine, respectively. Further investigations are still required to assess the usefulness of the simultaneous measurement of blood concentrations of HCQ and its three active metabolites for monitoring HCQ treatment and managing HCQ poisoning.