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Guignet M, White HS, Misra SN, Carrazana E, Rabinowicz AL. Development of a novel dosing paradigm to model diazepam rescue therapy in preclinical seizure and epilepsy models. Epilepsia Open 2024. [PMID: 38872261 DOI: 10.1002/epi4.12954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 04/10/2024] [Accepted: 04/17/2024] [Indexed: 06/15/2024] Open
Abstract
Diazepam is a cornerstone immediate-use antiseizure rescue therapy that may extend the duration between seizure clusters in people living with epilepsy. However, our mechanistic understanding of intermittent rescue therapy on disease progression is limited by the lack of suitable preclinical models. Specifically, the pharmacokinetics of diazepam varies widely between humans and laboratory animals. Here, we developed a novel repeat rescue therapy dosing paradigm in rats to maintain prolonged therapeutic concentrations seen in humans. Rats received three diazepam doses separated by 1 h (0.75, 1.5, or 3 mg/kg, intraperitoneal); plasma and brains were collected at 10 min and 1, 3, or 6 h following the last dose. Plasma and brain concentrations followed a dose-dependent increase with peak concentrations following the repeat 3 mg/kg paradigm (180 ng/mL) being equivalent to plasma levels observed in human studies with diazepam nasal spray. Increased brain-to-plasma ratios in this paradigm indicate that diazepam accumulation in the brain may be long-acting at the site of action. Overall, our repeat diazepam dosing paradigm mimics drug concentrations and accumulation seen in humans, offering a preclinical tool to study the impact of benzodiazepine rescue therapy on seizure-cluster biology in rodent models of epilepsy. PLAIN LANGUAGE SUMMARY: There is more to learn about how diazepam works in the brains of people who use it only when they have two or more seizures in 24 h (this is called a seizure cluster). Ethical studies in animals can be used to learn more about medicines in the body. In this study, we showed that three doses of diazepam in rats give about the same amount of the drug as one dose for a person. We can now test rats with epilepsy to see how the drug might work in people who take it when needed for seizure clusters.
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Affiliation(s)
- Michelle Guignet
- Center for Epilepsy Drug Discovery, Department of Pharmacy, University of Washington, Seattle, Washington, USA
| | - H Steve White
- Center for Epilepsy Drug Discovery, Department of Pharmacy, University of Washington, Seattle, Washington, USA
| | | | - Enrique Carrazana
- Neurelis, Inc., San Diego, California, USA
- John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA
| | - Adrian L Rabinowicz
- Neurelis, Inc., San Diego, California, USA
- Center for Molecular Biology and Biotechnology, Charles E. Schmidt College of Science, Florida Atlantic University, Boca Raton, Florida, USA
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Charalambous M, Muñana K, Patterson EE, Platt SR, Volk HA. ACVIM Consensus Statement on the management of status epilepticus and cluster seizures in dogs and cats. J Vet Intern Med 2024; 38:19-40. [PMID: 37921621 PMCID: PMC10800221 DOI: 10.1111/jvim.16928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 10/19/2023] [Indexed: 11/04/2023] Open
Abstract
BACKGROUND Seizure emergencies (ie, status epilepticus [SE] and cluster seizures [CS]), are common challenging disorders with complex pathophysiology, rapidly progressive drug-resistant and self-sustaining character, and high morbidity and mortality. Current treatment approaches are characterized by considerable variations, but official guidelines are lacking. OBJECTIVES To establish evidence-based guidelines and an agreement among board-certified specialists for the appropriate management of SE and CS in dogs and cats. ANIMALS None. MATERIALS AND METHODS A panel of 5 specialists was formed to assess and summarize evidence in the peer-reviewed literature with the aim to establish consensus clinical recommendations. Evidence from veterinary pharmacokinetic studies, basic research, and human medicine also was used to support the panel's recommendations, especially for the interventions where veterinary clinical evidence was lacking. RESULTS The majority of the evidence was on the first-line management (ie, benzodiazepines and their various administration routes) in both species. Overall, there was less evidence available on the management of emergency seizure disorders in cats in contrast to dogs. Most recommendations made by the panel were supported by a combination of a moderate level of veterinary clinical evidence and pharmacokinetic data as well as studies in humans and basic research studies. CONCLUSIONS AND CLINICAL RELEVANCE Successful management of seizure emergencies should include an early, rapid, and stage-based treatment approach consisting of interventions with moderate to preferably high ACVIM recommendations; management of complications and underlying causes related to seizure emergencies should accompany antiseizure medications.
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Affiliation(s)
| | - Karen Muñana
- North Carolina State UniversityRaleighNorth CarolinaUSA
| | | | | | - Holger A. Volk
- University of Veterinary Medicine HannoverHannoverGermany
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Charalambous M, Volk HA, Van Ham L, Bhatti SFM. First-line management of canine status epilepticus at home and in hospital-opportunities and limitations of the various administration routes of benzodiazepines. BMC Vet Res 2021; 17:103. [PMID: 33663513 PMCID: PMC7934266 DOI: 10.1186/s12917-021-02805-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 02/16/2021] [Indexed: 12/22/2022] Open
Affiliation(s)
- Marios Charalambous
- Small Animal Department, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium.
| | - Holger A Volk
- Department of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, 30559, Hannover, Germany
| | - Luc Van Ham
- Small Animal Department, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium
| | - Sofie F M Bhatti
- Small Animal Department, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium
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Ríos C, Farfán-Briseño AC, Manjarrez-Marmolejo J, Franco-Pérez J, Méndez-Armenta M, Nava-Ruiz C, Caballero-Chacón S, Ruiz-Diaz A, Baron-Flores V, Díaz-Ruiz A. Efficacy of dapsone administered alone or in combination with diazepam to inhibit status epilepticus in rats. Brain Res 2019; 1708:181-187. [DOI: 10.1016/j.brainres.2018.12.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/13/2018] [Accepted: 12/12/2018] [Indexed: 12/15/2022]
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Blades Golubovic S, Rossmeisl JH. Status epilepticus in dogs and cats, part 2: treatment, monitoring, and prognosis. J Vet Emerg Crit Care (San Antonio) 2017; 27:288-300. [DOI: 10.1111/vec.12604] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 07/09/2015] [Accepted: 09/03/2015] [Indexed: 12/14/2022]
Affiliation(s)
| | - John H. Rossmeisl
- Department of Small Animal Clinical Sciences; Virginia-Maryland Regional College of Veterinary Medicine; Blacksburg VA 24061
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Silveira AT, Albuquerque ACC, Lepera JS, Martins I. Diazepam influences urinary bioindicator of occupational toluene exposure. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2016; 48:191-196. [PMID: 27816004 DOI: 10.1016/j.etap.2016.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 10/14/2016] [Accepted: 10/15/2016] [Indexed: 06/06/2023]
Abstract
In the present study, we investigated the influence of diazepam (DZP) on the excretion of TOL by examining their urinary metabolites, hippuric acid (HA) and ortho-cresol (o-C). Male Wistar rats were exposed to TOL (20ppm) in a nose-only exposure chamber (6h/day, 5days/week for 6 weeks) with simultaneous administration of DZP (10mg/kg/day). Urinary o-C levels were determined by GC-MS, while HA, creatinine (CR), DZP and its metabolite, nordiazepam, were analysed by HPLC-DAD. The results of a Mann-Whitney U test showed that DZP influenced the urinary excretion of o-C (p<0.05). This pioneering study revealed that there was an interaction between DZP and TOL, probably by the inhibition of the CYP isoforms (CYP2B6, CYP2C8, CYP2E1, and CYP1A2) involved in the oxidative metabolism of the solvent. This is relevant information to be considered in the biomonitoring of occupational toluene exposure.
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Affiliation(s)
- Alberto Thalison Silveira
- Laboratory of Toxicant and Drug Analyses, Federal University of Alfenas, Unifal-MG, Alfenas, MG, Brazil
| | | | - José Salvador Lepera
- Laboratory of Occupational Toxicology, Faculty of Pharmaceutical Sciences of Araraquara - FCFAr, UNESP, Araraquara, SP, Brazil
| | - Isarita Martins
- Laboratory of Toxicant and Drug Analyses, Federal University of Alfenas, Unifal-MG, Alfenas, MG, Brazil.
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MacRae M, Kenkel WM, Kentner AC. Social rejection following neonatal inflammation is mediated by olfactory scent cues. Brain Behav Immun 2015; 49:43-8. [PMID: 25744105 DOI: 10.1016/j.bbi.2015.02.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 02/13/2015] [Accepted: 02/24/2015] [Indexed: 10/23/2022] Open
Abstract
Early-life exposure to inflammation has been associated with several behavioral and cognitive deficits detected in adulthood. However, early behavioral changes have not been well described in rodent models of infection, specifically with respect to social behavior. In the present work we show that lipopolysaccharide (LPS) challenge at 3 and 5days of age reduced overall social contact time in male juvenile rats, primarily mediated by the amount of contact they received from a novel conspecific. Given that there are important sensory, motor, and motivational components that underlie social interaction we sought to uncover the mechanism(s) responsible for the reduced social contact directed towards neonatal (n)LPS treated animals. Using an intranasal perfusion procedure, we induced a ZnSO4 lesion in a subset of novel conspecifics, effectively disrupting their olfactory processing via olfactory neuroepithelium degeneration. Overall, this procedure equalized the amount of social contact directed towards nLPS animals compared to nsaline rats. To determine whether nLPS disrupted auditory communication we evaluated ultrasonic vocalizations (USVs) for the total number and duration of calls, and the average duration and frequency from each vocalization recording. There were no differences in USVs across treatment groups. Treating nLPS rats with diazepam maintained the level of social contact they initiated, compared to the stress-induced decrease observed in their saline treated counterparts. However, diazepam did not stabilize the amount of contact directed towards them. Together, this indicates that neither vocalized motor pathways nor anxiety cues, mediated by auditory/motor communication, are involved in the social deficits following nLPS. Instead, our data suggest that olfactory indicators, likely mediated through microbiota/immunomodulatory scent signals underlie the reductions in social contact that follow neonatal inflammation.
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Affiliation(s)
- M MacRae
- School of Arts & Sciences, Health Psychology Program, MCPHS University (formerly Massachusetts College of Pharmacy & Health Sciences), Boston, MA 02115, United States
| | - W M Kenkel
- Department of Psychology, Northeastern University, Boston, MA 02115, United States
| | - A C Kentner
- School of Arts & Sciences, Health Psychology Program, MCPHS University (formerly Massachusetts College of Pharmacy & Health Sciences), Boston, MA 02115, United States.
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Shakarjian MP, Ali MS, Velíšková J, Stanton PK, Heck DE, Velíšek L. Combined diazepam and MK-801 therapy provides synergistic protection from tetramethylenedisulfotetramine-induced tonic-clonic seizures and lethality in mice. Neurotoxicology 2015; 48:100-8. [PMID: 25783504 DOI: 10.1016/j.neuro.2015.03.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/07/2015] [Accepted: 03/07/2015] [Indexed: 12/21/2022]
Abstract
The synthetic rodenticide, tetramethylenedisulfotetramine (TMDT), is a persistent and highly lethal GABA-gated Cl(-) channel blocker. TMDT is clandestinely produced, remains popular in mainland China, and causes numerous unintentional and deliberate poisonings worldwide. TMDT is odorless, tasteless, and easy to manufacture, features that make it a potential weapon of terrorism. There is no effective treatment. We previously characterized the effects of TMDT in C57BL/6 mice and surveyed efficacies of GABAergic and glutamatergic anticonvulsant treatments. At 0.4 mg/kg i.p., TMDT produced neurotoxic symptomatology consisting of twitches, clonic and tonic-clonic seizures, often progressing to status epilepticus and death. If administered immediately after the occurrence of the first clonic seizure, the benzodiazepine diazepam (DZP) effectively prevented all subsequent seizure symptoms, whereas the NMDA receptor antagonist dizocilpine (MK-801) primarily prevented tonic-clonic seizures. The latter agent, however, appeared to be more effective at preventing delayed death. The present study further explored these phenomena, and characterized the therapeutic actions of DZP and MK-801 as combinations. Joint treatment with both DZP and MK-801 displayed synergistic protection against tonic-clonic seizures and 24 h lethality as determined by isobolographic analysis. Clonic seizures, however, remained poorly controlled. A modification of the treatment regimen, where DZP was followed 10 min later by MK-801, yielded a reduction in both types of seizures and improved overall outcome. Simultaneous monitoring of subjects via EEG and videography confirmed effectiveness of this sequential regimen. We conclude that TMDT blockage at GABAA receptors involves early activation of NMDA receptors, which contribute to persistent ictogenic activity. Our data predict that a sequential combination treatment with DZP followed by MK-801 will be superior to either individual therapy with, or simultaneous administration of, these two agents in treating TMDT poisoning.
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Affiliation(s)
- Michael P Shakarjian
- Department of Environmental Health Science, School of Health Sciences and Practice, Institute of Public Health, New York Medical College, Valhalla, NY 10595, United States; Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, United States; Department of Medicine, Division of Pulmonary and Critical Care Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, United States.
| | - Mahil S Ali
- Department of Environmental Health Science, School of Health Sciences and Practice, Institute of Public Health, New York Medical College, Valhalla, NY 10595, United States.
| | - Jana Velíšková
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, United States; Department of Obstetrics and Gynecology, New York Medical College, Valhalla, NY 10595, United States; Department of Neurology, New York Medical College, Valhalla, NY 10595, United States.
| | - Patric K Stanton
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, United States; Department of Neurology, New York Medical College, Valhalla, NY 10595, United States.
| | - Diane E Heck
- Department of Environmental Health Science, School of Health Sciences and Practice, Institute of Public Health, New York Medical College, Valhalla, NY 10595, United States.
| | - Libor Velíšek
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, United States; Department of Neurology, New York Medical College, Valhalla, NY 10595, United States; Department of Pediatrics, New York Medical College, Valhalla, NY 10595, United States.
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Wright BT, Gluszek CF, Heldt SA. The effects of repeated zolpidem treatment on tolerance, withdrawal-like symptoms, and GABAA receptor mRNAs profile expression in mice: comparison with diazepam. Psychopharmacology (Berl) 2014; 231:2967-79. [PMID: 24531568 DOI: 10.1007/s00213-014-3473-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 01/26/2014] [Indexed: 10/25/2022]
Abstract
RATIONALE Zolpidem is a short-acting, non-benzodiazepine hypnotic that acts as a full agonist at α1-containing GABAA receptors. Overall, zolpidem purportedly has fewer instances of abuse and dependence than traditionally used benzodiazepines. However, several studies have shown that zolpidem may be more similar to benzodiazepines in terms of behavioral tolerance and withdrawal symptoms. OBJECTIVES In the current study, we examined whether subchronic zolpidem or diazepam administration produced deficits in zolpidem's locomotor-impairing effects, anxiety-like behaviors, and changes in GABAAR subunit messenger RNA (mRNA). METHODS Mice were given subchronic injections of either zolpidem (10 mg/kg), diazepam (20 mg/kg), or vehicle twice daily for 7 days. On day 8, mice were given a challenge dose of zolpidem (2 mg/kg) or vehicle before open field testing. Another set of mice underwent the same injection regimen but were sacrificed on day 8 for qRT-PCR analysis. RESULTS We found that subchronic zolpidem and diazepam administration produced deficits in the acute locomotor-impairing effects of zolpidem and increased anxiety-like behaviors 1 day after drug termination. In addition, we found that subchronic treatment of zolpidem and diazepam induced distinct but overlapping GABAAR subunit mRNA changes in the cortex but few changes in the hippocampus, amygdala, or prefrontal cortex. Levels of mRNA measured in separate mice after a single injection of either zolpidem or diazepam revealed no mRNA changes. CONCLUSIONS In mice, subchronic treatment of zolpidem and diazepam can produce deficits in the locomotor-impairing effects of zolpidem, anxiety-like withdrawal symptoms, and subunit-specific mRNA changes.
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Affiliation(s)
- Brittany T Wright
- The Department of Anatomy and Neurobiology, Neuroscience Institute, University of Tennessee Health Science Center, 855 Monroe Ave, Memphis, TN, 38163, USA
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Ma LL, Freret T, Lange M, Bourgine J, Coquerel A, Lelong-Boulouard V. Benzodiazepines increase the reward effects of buprenorphine in a conditioned place preference test in the mouse. Fundam Clin Pharmacol 2014; 28:681-9. [DOI: 10.1111/fcp.12072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 02/12/2014] [Accepted: 03/06/2014] [Indexed: 11/30/2022]
Affiliation(s)
- Lin-Lin Ma
- Normandie University; CS 14032 Cedex 5 Caen France
- UCBN; COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
- Inserm; U 1075 COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
| | - Thomas Freret
- Normandie University; CS 14032 Cedex 5 Caen France
- UCBN; Groupe Mémoire et Plasticité comportementale (GMPc) EA 4259; UFR des Sciences Pharmaceutiques, Boulevard Becquerel; 14032 Caen France
| | - Mathilde Lange
- CHU de Caen, Service de Pharmacologie; Avenue de la Côte de Nacre 14033 Caen France
| | - Joanna Bourgine
- Normandie University; CS 14032 Cedex 5 Caen France
- UCBN; COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
- Inserm; U 1075 COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
- CHU de Caen, Service de Pharmacologie; Avenue de la Côte de Nacre 14033 Caen France
| | - Antoine Coquerel
- Normandie University; CS 14032 Cedex 5 Caen France
- UCBN; COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
- Inserm; U 1075 COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
- CHU de Caen, Service de Pharmacologie; Avenue de la Côte de Nacre 14033 Caen France
- Centres régionaux de pharmacovigilance et d'addictovigilance; CHU Caen; 14033 Caen France
| | - Véronique Lelong-Boulouard
- Normandie University; CS 14032 Cedex 5 Caen France
- UCBN; COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
- Inserm; U 1075 COMETE; UFR de Médecine; Avenue de la Côte de Nacre CS 14032 Cedex 5 Caen France
- CHU de Caen, Service de Pharmacologie; Avenue de la Côte de Nacre 14033 Caen France
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Chevillard L, Declèves X, Baud FJ, Risède P, Mégarbane B. Respiratory effects of diazepam/methadone combination in rats: a study based on concentration/effect relationships. Drug Alcohol Depend 2013; 131:298-307. [PMID: 23332448 DOI: 10.1016/j.drugalcdep.2012.12.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 12/12/2012] [Accepted: 12/18/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND Methadone may cause respiratory depression and fatalities. Concomitant use of benzodiazepines in methadone-treated patients for chronic pain or as maintenance therapy for opiate abuse is common. However, the exact contribution of benzodiazepines to methadone-induced respiratory toxicity remains debatable. METHODS We investigated the respiratory effects of the combination diazepam (20mg/kg)/methadone (5mg/kg) in the rat, focusing on methadone concentration/effect relationships. Respiratory effects were studied using arterial blood gases and whole-body plethysmography. Plasma concentrations of both R- and S-methadone enantiomers were measured using high-performance liquid chiral chromatography coupled to mass spectrometry. To clarify mechanisms of diazepam/methadone interaction, methadone metabolism was investigated in vitro using rat liver microsomes. RESULTS Diazepam/methadone co-administration significantly increased methadone-related effects on inspiratory time (p<0.001) but did not significantly alter the other respiratory parameters when compared with methadone alone, despite significant increase in the area under the curve of plasma R-methadone concentrations measured during 240 min (p<0.05). Diazepam/methadone co-incubation with microsomes in vitro resulted in a significant inhibition of methadone metabolism (p<0.01), with 50%-inhibitory diazepam concentrations of 25.02 ± 0.18 μmol/L and 25.18 ± 0.23 μmol/L for R- and S-methadone, respectively. CONCLUSION We concluded that co-administration of high-doses of diazepam and methadone in rats is not responsible for additional respiratory depression in comparison to methadone alone, despite significant metabolic interaction between the drugs. In humans, although our experimental data may suggest the relative safety of benzodiazepine/methadone co-prescription, physicians should remain cautious as other underlying conditions may enhance this drug-drug interaction.
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Affiliation(s)
- Lucie Chevillard
- INSERM U705, CNRS UMR8206, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, Neuropsychopharmacologie des addictions, Paris, France.
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Shakarjian MP, Velíšková J, Stanton PK, Velíšek L. Differential antagonism of tetramethylenedisulfotetramine-induced seizures by agents acting at NMDA and GABA(A) receptors. Toxicol Appl Pharmacol 2012; 265:113-21. [PMID: 23022509 DOI: 10.1016/j.taap.2012.08.037] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 08/13/2012] [Accepted: 08/30/2012] [Indexed: 01/08/2023]
Abstract
Tetramethylenedisulfotetramine (TMDT) is a highly lethal neuroactive rodenticide responsible for many accidental and intentional poisonings in mainland China. Ease of synthesis, water solubility, potency, and difficulty to treat make TMDT a potential weapon for terrorist activity. We characterized TMDT-induced convulsions and mortality in male C57BL/6 mice. TMDT (ip) produced a continuum of twitches, clonic, and tonic-clonic seizures decreasing in onset latency and increasing in severity with increasing dose; 0.4mg/kg was 100% lethal. The NMDA antagonist, ketamine (35mg/kg) injected ip immediately after the first TMDT-induced seizure, did not change number of tonic-clonic seizures or lethality, but increased the number of clonic seizures. Doubling the ketamine dose decreased tonic-clonic seizures and eliminated lethality through a 60min observation period. Treating mice with another NMDA antagonist, MK-801, 0.5 or 1mg/kg ip, showed similar effects as low and high doses of ketamine, respectively, and prevented lethality, converting status epilepticus EEG activity to isolated interictal discharges. Treatment with these agents 15min prior to TMDT administration did not increase their effectiveness. Post-treatment with the GABA(A) receptor allosteric enhancer diazepam (5mg/kg) greatly reduced seizure manifestations and prevented lethality 60min post-TMDT, but ictal events were evident in EEG recordings and, hours post-treatment, mice experienced status epilepticus and died. Thus, TMDT is a highly potent and lethal convulsant for which single-dose benzodiazepine treatment is inadequate in managing electrographic seizures or lethality. Repeated benzodiazepine dosing or combined application of benzodiazepines and NMDA receptor antagonists is more likely to be effective in treating TMDT poisoning.
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Affiliation(s)
- Michael P Shakarjian
- Department of Environmental Health Science, School of Health Sciences and Practice, Institute of Public Health, New York Medical College, Valhalla, NY, 10595, USA.
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Tolerance liability of diazepam is dependent on the dose used for protracted treatment. Pharmacol Rep 2012; 64:1116-25. [DOI: 10.1016/s1734-1140(12)70908-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 05/23/2012] [Indexed: 11/18/2022]
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Mohamed WR, El Sherbiny GA, Zaki HF, El Sayed ME. Possible modulation of the antidiabetic effect of rosiglitazone by buspirone. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.bfopcu.2012.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Diazepam autoinjector intramuscular delivery system versus diazepam rectal gel: A pharmacokinetic comparison. Epilepsy Res 2011; 93:11-6. [DOI: 10.1016/j.eplepsyres.2010.10.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 09/29/2010] [Accepted: 10/03/2010] [Indexed: 11/24/2022]
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Tolerance, sensitization and dependence to diazepam in Balb/c mice exposed to a novel open space anxiety test. Behav Brain Res 2010; 209:154-64. [PMID: 20117142 DOI: 10.1016/j.bbr.2010.01.039] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 01/18/2010] [Accepted: 01/24/2010] [Indexed: 02/05/2023]
Abstract
Balb/c mice were exposed to an elevated platform that is extended on two opposite sides with lowered steep slopes. They were tested for 12min per session in 6 successive days. They received i.p. administration of either saline or one dose of diazepam (DZP 0.5, 1, 3mg/kg) in sessions 1-3, and saline in sessions 4 and 5. All groups of mice received a single dose of DZP (1mg/kg) in session 6. DZP produced inverted U-shaped dose-responses on the number of entries into different areas of the apparatus, with a peak in mean response at 1mg/kg whereas its effect on the duration of entries was mostly comparable between the 3 doses. It increased the number of crossings on the surface of the platform and facilitated entries onto the slopes. DZP-treated mice crossed frequently onto and spent longer time on the slopes in sessions 1-3 whereas saline-treated mice remained on the platform in sessions 1-6. Withdrawal of DZP in sessions 4-5 increased the latency of first entry and decreased the number and duration of entries onto the slopes which was reversed with the administration of 1mg/kg of DZP in the next session. This ON-OFF the drug may be due to the half-life of DZP which is very short in mice and rats ( approximately 0.88h). It also indicates that DZP-treated mice did not benefit from previous experience of entries onto the slopes which suggests a possible "state-dependent" effect. Administration of DZP after repeated exposures to the test did not facilitate entries onto the slopes but instead increased significantly the number of crossings on the surface of the platform; this increase was much higher than that observed in mice initially treated with DZP and exposed to the test. There is no evidence of habituation in saline-treated mice: the number of crossings on the platform was comparable between the first 5 sessions of the test. These results demonstrate that repeated exposures to the same anxiogenic environment resulted in avoidance responses developing tolerance and approach responses developing sensitization. They suggest that tolerance and sensitization are two opposite sides of the habituation process to the same stimulus and may account for the maintained state of anxiety.
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Shikanai H, Izumi T, Matsumoto M, Togashi H, Yamaguchi T, Yoshida T, Yoshioka M. Diazepam-Induced Increases of Synaptic Efficacy in the Hippocampal – Medial Prefrontal Cortex Pathway Are Associated With Its Anxiolytic-like Effect in Rats. J Pharmacol Sci 2010; 114:341-6. [DOI: 10.1254/jphs.10182fp] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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18
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Watterson JH, Botman JE. Detection of acute diazepam exposure in bone and marrow: influence of tissue type and the dose-death interval on sensitivity of detection by ELISA with liquid chromatography tandem mass spectrometry confirmation. J Forensic Sci 2009; 54:708-14. [PMID: 19432747 DOI: 10.1111/j.1556-4029.2009.00998.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enzyme-linked immunosorbent assay (ELISA) and liquid chromatography tandem mass spectrometry (LC/MS/MS) were used to detect diazepam exposure in skeletal tissues of rats (n = 15) given diazepam acutely (20 mg/kg, i.p.), and killed at various times postdose. Marrow, epiphyseal, and diaphyseal bone were isolated from extracted femora. Bone was cleaned, ground, and incubated in methanol. Marrow underwent ultrasonic homogenization. Extracts and homogenates were diluted in phosphate buffer, and then underwent solid-phase extraction and ELISA. Relative sensitivity of detection was examined in terms of relative decrease in absorbance (ELISA) and binary classification sensitivity (ELISA and LC/MS/MS). Overall, the data showed differences in relative sensitivity of detection of diazepam exposure in different tissue types (marrow > epiphyseal bone > diaphyseal bone), which is suggestive of heterogenous distribution in these tissues, and a decreasing sensitivity with increasing dose-death interval. Thus, the tissue type sampled and dose-death interval may contribute to the probability of detection of diazepam exposure in skeletal tissues.
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Affiliation(s)
- James H Watterson
- Forensic Toxicology Research Laboratory, Department of Forensic Science, Laurentian University, 935 Ramsey Lake Rd. Sudbury, Ontario, P3E 2C6, Canada.
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19
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Allison C, Pratt JA. Differential effects of two chronic diazepam treatment regimes on withdrawal anxiety and AMPA receptor characteristics. Neuropsychopharmacology 2006; 31:602-19. [PMID: 15970947 DOI: 10.1038/sj.npp.1300800] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Withdrawal from chronic benzodiazepines is associated with increased anxiety and seizure susceptibility. Neuroadaptive changes in neural activity occur in limbo-cortical structures although changes at the level of the GABA(A) receptor do not provide an adequate explanation for these functional changes. We have employed two diazepam treatment regimes known to produce differing effects on withdrawal aversion in the rat and examined whether withdrawal-induced anxiety was accompanied by changes in AMPA receptor characteristics. Rats were given 28 days treatment with diazepam by the intraperitoneal (i.p.) route (5 mg/kg) and the subcutaneous (s.c.) route (15 mg/kg). Withdrawal anxiety in the elevated plus maze was evident in the group withdrawn from chronic s.c. diazepam (relatively more stable plasma levels) but not from the chronic i.p. group (fluctuating daily plasma levels). In the brains of these rats, withdrawal anxiety was accompanied by increased [3H]Ro48 8587 binding in the hippocampus and thalamus, and decreased GluR1 and GluR2 subunit mRNA expression in the amygdala (GluR1 and GluR2) and cortex (GluR1). The pattern of changes was different in the chronic i.p. group where in contrast to the chronic s.c. group, there was reduced [3H]Ro48 8587 binding in the hippocampus and no alterations in GluR1 and GluR2 subunit expression in the amygdala. While both groups showed reduced GluR1 mRNA subunit expression in the cortex overall, only the agranular insular cortex exhibited marked reductions following chronic i.p. diazepam. Striatal GluR2 mRNA expression was increased in the i.p. group but not the s.c. group. Taken together, these data are consistent with differential neuroadaptive processes in AMPA receptor plasticity being important in withdrawal from chronic benzodiazepines. Moreover, these processes may differ both at a regional and receptor function level according to the behavioral manifestations of withdrawal.
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Affiliation(s)
- Claire Allison
- Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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20
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Marrs TC. The role of diazepam in the treatment of nerve agent poisoning in a civilian population. ACTA ACUST UNITED AC 2005; 23:145-57. [PMID: 15862082 DOI: 10.2165/00139709-200423030-00002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The main site of action of diazepam, as with other benzodiazepines, is at the GABA(A) receptor, although it has been suggested that some of the potentially beneficial actions of diazepam in nerve agent poisoning are mediated through other means. It is likely that convulsions may have long-term sequelae in the central nervous system, because of damage by anoxia and/or excitotoxicity. Numerous pharmacodynamic studies of the action of diazepam in animals experimentally poisoned with nerve agents have been undertaken. In nearly all of these, diazepam has been studied in combination with other antidotes, such as atropine and/or pyridinium oximes, sometimes in combination with pyridostigmine pretreatment. These studies show that diazepam is an efficacious anticonvulsant in nerve agent poisoning. There is considerable experimental evidence to support the hypothesis that diazepam (and other anticonvulsants) may prevent structural damage to the central nervous system as evidenced by neuropathological changes such as neuronal necrosis at autopsy. In instances of nerve agent poisoning during terrorist use in Japan, diazepam seems to have been an effective anticonvulsant. Consequently, the use of diazepam is an important part of the treatment regimen of nerve agent poisoning, the aim being to prevent convulsions or reduce their duration. Diazepam should be given to patients poisoned with nerve agents whenever convulsions or muscle fasciculation are present. In severe poisoning, diazepam administration should be considered even before these complications occur. Diazepam is also useful as an anxiolytic in those exposed to nerve agents.
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Affiliation(s)
- Timothy C Marrs
- Food Standards Agency, London and National Poisons Information Service, (Birmingham Centre), City Hospital, Birmingham, UK
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21
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Wang J, Shen X, Fenyk-Melody J, Pivnichny JV, Tong X. Simple and sensitive liquid chromatography/tandem mass spectrometry method for the determination of diazepam and its major metabolites in rat cerebrospinal fluid. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2003; 17:519-525. [PMID: 12621612 DOI: 10.1002/rcm.942] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Diazepam (DZP) is one of the most commonly prescribed drugs for treating status epilepticus (SE). A simple, sensitive and selective LC/MS/MS method with a wide linear calibration range was developed to quantify DZP and its major metabolites, N-desmethyldiazepam (DMDZP), temazepam (TZP), and oxazepam (OZP), in rat cerebrospinal fluid (CSF). The method was used to simultaneously determine the concentrations of all analytes in a small sample volume (as little as 25 microL) of rat CSF. The lower limits of quantification (LLOQ) of the method are 0.04 ng/mL for DZP and 0.1 ng/mL for its metabolites. The calibration range is 0.04-200 ng/mL for DZP and 0.1-200 ng/ml for the metabolites. All intra- and inter-assay coefficients of variation (%CV) and mean percent errors of the method are less than 12%. This method successfully addresses the need to determine low therapeutic drug concentrations in small physiological samples, namely rat CSF. Moreover, it can be used to investigate the distribution of the drug and its metabolites among blood plasma, brain tissue, and CSF in pharmacokinetic and pharmacodynamic studies in a variety of laboratory animals. With respect to animal experiments involving assays in CSF, this method addresses two of the three criteria of Russell and Bruch (Principles of Humane Experimental Techniques, 1959, Methuen and Co., London) for minimizing animal use, namely refinement and reduction.
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Affiliation(s)
- Junying Wang
- Department of Basic Chemistry, Merck & Co Inc, Rahway, NJ 07065, USA.
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Allison C, Claase LA, Pratt JA. Diazepam withdrawal-induced anxiety and place aversion in the rat: differential effects of two chronic diazepam treatment regimes. Behav Pharmacol 2002; 13:417-25. [PMID: 12394418 DOI: 10.1097/00008877-200209000-00015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The ability of the benzodiazepine antagonist flumazenil to precipitate a withdrawal subjective state in rats receiving chronic diazepam was investigated in a biased conditioned place aversion (CPA) procedure. Conditioning with flumazenil (10 mg/kg i.p.) in rats receiving chronic diazepam subcutaneously (s.c. in oil, 15 mg/kg/day for 28 days) but not intraperitoneally (i.p., 5 mg/kg for 28 days) resulted in the formation of a conditioned place aversion. These results indicate that precipitated withdrawal from diazepam injected s.c. but not i.p. produces a negative subjective state and that the conditioned place aversion paradigm may be useful in detecting the negative subjective effects of diazepam withdrawal. In parallel studies, the same s.c. treatment protocol produced an anxiogenic effect in the elevated plus-maze on spontaneous diazepam withdrawal, whereas rats treated with the i.p. protocol displayed no signs of withdrawal anxiety. The results of the present study are consistent with the interpretation that rats withdrawn from chronic i.p. diazepam did not demonstrate a CPA due to the 'repeated withdrawal' experiences induced by the i.p. injection route attenuating the subsequent ability of flumazenil to precipitate a subjective withdrawal state. Pharmacokinetic evidence and previous evidence showing that repeated withdrawal from diazepam in mice attenuates the aversive effects of the withdrawal experience in a conditioned taste aversion (CTA) paradigm support this interpretation.
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Affiliation(s)
- C Allison
- Department of Physiology and Pharmacology, University of Strathclyde, Strathclyde Institute for Biomedical Sciences, Glasgow, UK
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Affiliation(s)
- A S Lockey
- Accident and Emergency Department, York District Hospital, UK.
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Tong X, Patsalos PN. A microdialysis study of the novel antiepileptic drug levetiracetam: extracellular pharmacokinetics and effect on taurine in rat brain. Br J Pharmacol 2001; 133:867-74. [PMID: 11454660 PMCID: PMC1572849 DOI: 10.1038/sj.bjp.0704141] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2000] [Revised: 04/30/2001] [Accepted: 04/30/2001] [Indexed: 11/08/2022] Open
Abstract
Using a rat model which allows serial blood sampling and concurrent brain microdialysis sampling, we have investigated the temporal kinetic inter-relationship of levetiracetam in serum and brain extracellular fluid (frontal cortex and hippocampus) following systemic administration of levetiracetam, a new antiepileptic drug. Concurrent extracellular amino acid concentrations were also determined. After administration (40 or 80 mg kg(-1)), levetiracetam rapidly appeared in both serum (T(max), 0.4 - 0.7 h) and extracellular fluid (T(max), 2.0 - 2.5 h) and concentrations rose linearly and dose-dependently, suggesting that transport across the blood-brain barrier is rapid and not rate-limiting. The serum free fraction (free/total serum concentration ratio; mean+/-s.e.mean range 0.93 - 1.05) was independent of concentration and confirms that levetiracetam is not bound to blood proteins. The kinetic profiles for the hippocampus and frontal cortex were indistinguishable suggesting that levetiracetam distribution in the brain is not brain region specific. However, t(1/2) values were significantly larger than those for serum (mean range, 3.0 - 3.3 h vs 2.1 - 2.3 h) and concentrations did not attain equilibrium with respect to serum. Levetiracetam (80 mg kg(-1)) was associated with a significant reduction in taurine in the hippocampus and frontal cortex. Other amino acids were unaffected by levetiracetam. Levetiracetam readily and rapidly enters the brain without regional specificity. Its prolonged efflux from and slow equilibration within the brain may explain, in part, its long duration of action. The concurrent changes in taurine may contribute to its mechanism of action.
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Affiliation(s)
- X Tong
- Pharmacology and Therapeutics Unit, University Department of Clinical Neurology, Institute of Neurology, Queen Square, London
| | - P N Patsalos
- Pharmacology and Therapeutics Unit, University Department of Clinical Neurology, Institute of Neurology, Queen Square, London
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Cherry JA, Thompson BE, Pho V. Diazepam and rolipram differentially inhibit cyclic AMP-specific phosphodiesterases PDE4A1 and PDE4B3 in the mouse. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1518:27-35. [PMID: 11267656 DOI: 10.1016/s0167-4781(01)00164-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Cyclic AMP is hydrolyzed by members of at least eight classes of cyclic nucleotide phosphodiesterases (PDEs). Although it has been reported that cyclic AMP PDE activity in mammalian tissues can be inhibited by benzodiazepines, it has not been conclusively demonstrated that members of the class of cyclic AMP-specific, rolipram-inhibitable PDEs (PDE4s) are targets for these drugs. Moreover, no PDE4s expressed in mice have been characterized. To address these issues, we isolated two cDNAs representing homologues of PDE4A1 and PDE4B3 from a mouse brain library. After transient transfection in human embryonic kidney (HEK) 293 cells, the mouse PDEs hydrolyzed cyclic AMP with a low K(m) and were inhibited by rolipram; both are properties typical of other mammalian PDE4 enzymes. In addition, we found that diazepam inhibited cyclic AMP hydrolysis by the mouse PDE4 subtypes. Interestingly, PDE4B was significantly more sensitive to inhibition by both rolipram and diazepam than the PDE4A subtype. This is the first demonstration that recombinantly expressed PDE4s are inhibited by diazepam, and should facilitate future studies with mouse models of depression and anxiety.
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Affiliation(s)
- J A Cherry
- Department of Psychology and Laboratory of Molecular Neurobiology and Behavior, 64 Cummington Street, Boston University, 02215, Boston, MA, USA.
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Walker MC, Tong X, Perry H, Alavijeh MS, Patsalos PN. Comparison of serum, cerebrospinal fluid and brain extracellular fluid pharmacokinetics of lamotrigine. Br J Pharmacol 2000; 130:242-8. [PMID: 10807660 PMCID: PMC1572088 DOI: 10.1038/sj.bjp.0703337] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We investigated the rate of penetration into and the intra-relationship between the serum, cerebrospinal fluid (CSF) and regional brain extracellular fluid (bECF) compartments following systemic administration of lamotrigine in rat. The serum pharmacokinetics were biphasic with an initial distribution phase, (half-life approximately 3 h), and then a prolonged elimination phase of over 30 h. The serum pharmacokinetics were linear over the range 10 - 40 mg kg(-1). Using direct sampling of CSF with concomitant serum sampling, the calculated penetration half-time into CSF was 0.42+/-0.15 h. At equilibrium, the CSF to total serum concentration ratio (0.61+/-0.02) was greater than the free to total serum concentration (0.39+/-0.01). Using in vivo recovery corrected microdialysis sampling in frontal cortex and hippocampus with concomitant serum sampling, the calculated penetration half-time of lamotrigine into bECF, 0.51+/-0.11 h, was similar to that for CSF and was not area or dose dependent. At equilibrium, the bECF to total serum concentration ratio (0.40+/-0.04) was similar to the free to total serum concentration (0.39+/-0.01), and did not differ between hippocampus and frontal cortex. The species specific serum kinetics can explain the prolonged action of lamotrigine in rat seizure models. Lamotrigine has a relatively slow penetration into both CSF and bECF compartments compared with antiepileptic drugs used in acute seizures. Furthermore, the free serum drug concentration is not the sole contributor to the CSF compartment, and the CSF concentration is an overestimate of the bECF concentration of lamotrigine.
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Affiliation(s)
- M C Walker
- Epilepsy Research Group, Pharmacology and Therapeutics Unit, University Department of Clinical Neurology, Institute of Neurology, Queen Square, London WC1N 3BG.
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Nagaki S, Ratnaraj N, Patsalos PN. Blood and cerebrospinal fluid pharmacokinetics of primidone and its primary pharmacologically active metabolites, phenobarbital and phenylethylmalonamide in the rat. Eur J Drug Metab Pharmacokinet 1999; 24:255-64. [PMID: 10716065 DOI: 10.1007/bf03190029] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Primidone is a clinically useful antiepileptic drug that is metabolised to two pharmacologically active metabolites phenobarbital and phenylethylmalonamide. As data on the inter-relationship between the systemic and central nervous system pharmacokinetics of primidone and its metabolites are sparse, we have investigated their temporal inter-relationship using a freely behaving rat model which allows repeated sampling of blood (100 microl) and cerebrospinal fluid (CSF; 20 microl). After administration, by intraperitoneal injection (50, 100 or 200 mg/kg), primidone rapidly appeared in both serum (Tmax mean range 1.5-2.5 h) and CSF (Tmax mean range 2.0-3.5 h), suggesting ready penetration of the blood-brain-barrier. This was also the case for phenylethylmalonamide and phenobarbital but peak concentration occurred later. Primidone, phenylethylmalonamide and phenobarbital concentrations rose linearly and dose-dependently in both serum and CSF. The mean free fraction (free/total concentration ratio) for primidone, phenylethylmalonamide and phenobarbital was 0.86, 0.97 and 0.88, respectively, and, as their respective mean CSF/serum ratio values were 0.73, 1.06 and 0.65, it would suggest that equilibration between the blood and CSF compartments is rapid. CSF mean t(1/2) values for primidone, phenylethylmalonamide and phenobarbital were similar to those of sera and essentially paralleled the pattern seen in sera.
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Affiliation(s)
- S Nagaki
- Pharmacolgy and Therapeutics Unit, University Department of Clinical Neurology, Institute of Neurology, London, UK
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Doheny HC, Ratnaraj N, Whittington MA, Jefferys JG, Patsalos PN. Blood and cerebrospinal fluid pharmacokinetics of the novel anticonvulsant levetiracetam (ucb L059) in the rat. Epilepsy Res 1999; 34:161-8. [PMID: 10210031 DOI: 10.1016/s0920-1211(98)00104-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The temporal pharmacokinetic interrelationship of levetiracetam in blood and cerebrospinal fluid (CSF) was studied after acute intraperitoneal administration of levetiracetam (20, 40 and 80 mg/kg), using an animal model that permits concurrent blood and CSF sampling in freely moving rats. After administration, levetiracetam rapidly appeared in both serum (time to maximum concentration (Tmax) mean range 0.25 0.50 h) and CSF (Tmax mean range 1.33-1.92 h), suggesting ready penetration of the blood brain barrier. Both serum and CSF levetiracetam concentrations rose essentially linearly and dose-dependently, suggesting that transport across the blood-brain barrier is not rate limiting over the levetiracetam concentration range observed in the present study. However, while apparent elimination half-life (t1/2) values for both serum and CSF were dose-independent (mean value range 1.8-2.8 and 4.4-4.9 h, respectively), t1/2 values for CSF were significantly larger. As the serum free/total serum levetiracetam concentration ratio (free fraction) was 1.01+/-0.02 (mean+/-S.E.M.), it can be concluded that levetiracetam is not protein bound. Furthermore, the free fraction was indistinguishable from that of the CSF/serum levetiracetam concentration ratio at equilibrium. It can be concluded that the kinetics of levetiracetam, in the rat, is simple and, thus, dosing strategies in studies designed to elucidate its mechanism of action should be straightforward.
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Affiliation(s)
- H C Doheny
- University Department of Clinical Neurology, Institute of Neurology, London, UK
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