Hypnotic, anticonvulsant and muscle relaxant effects of Rubus brasiliensis. Involvement of GABA(A)-system

Rubus brasiliensis hexanic fraction induced anxiolysis in rodents, which was reversed by flumazenil, a specific GABA(A)-benzodiazepine receptor antagonist (Nogueira et al., 1998a,b). Then, we investigated if this hexanic fraction was able to induce hypnotic, anticonvulsant and muscle relaxant effects, and the involvement of GABA(A)-system. The hexanic fraction (50, 100, 150 and 300 mg/kg, vo) was administered to male Swiss mice, 30 min before the tests. Only the dose of 300 mg/kg of this fraction decreased the latency and increased sleeping time in the barbituric-hypnosis test (sodium pentobarbital, 30 mg/kg, ip), prevented the pentylenetetrazol seizures (70 mg/kg, ip) and induced muscle relaxant (inclined plane) in 100% of animals. These effects were reversed by flumazenil (3 mg/kg, ip). In conclusion: (1) R. brasiliensis hexanic fraction induced hypnotic, anticonvulsant and muscle relaxant effects, in mice, and the GABA(A)-benzodiazepine receptor may play an important role in the effects of this fraction; (2) it is strongly suggested that this fraction contains a benzodiazepine-like principle. (C) 2000 Elsevier B.V. Ireland Ltd. All rights reserved.

Therapeutic response of benzodiazepine, orphenadrine citrate and occlusal splint association in TMD pain

Loss of function, muscle inflammation, and pain are some of the signs and symptoms of temporomandibular dysfunction (TMD). Pharmacological strategies to minimize the clinical manifestation of these disorders often focus on blocking or inhibiting the pain-causing symptom. Resources such as muscle-relaxants, anxiety-relief drugs, and splint therapy are often used to reduce muscular hyperactivity related to TMD muscle pain. This study compares the effect of a randomly ordered association of occlusal splint therapy (S), nonsteroid anti-inflammatory with a muscle-relaxant drug (orphenadrine citrate) (O), and an anxiety-relief drug (benzodiazepine) (B), to ease painful TMD muscle symptoms. Clinical and anamnestic analyses were recorded in accordance with the Helkimo TMD index and applied before and after treatments. Twenty-one group two Helkimo TMD adult female patients were treated, all of whom were subjected to the three random therapeutic associations proposed: SBO, BOS, and OSB. The same operator applied the three specific associations over a period of 21 days in the proposed sequence, seven days for each therapy. The results show that all the groups presented the best results in terms of relief from pain after the therapeutic association (28.5% showed a decrease and 47.6% showed an absence of symptoms). No significant difference was observed among association therapeutic protocols. Copyright © 2003 by CHROMA, Inc.

Polimorfismos del gen Butirilcolinesterasa responsables de reacciones adversas en pacientes consumidores de “cocaína”

La butirilcolinesterasa humana (BChE; EC 3.1.1.8) es una enzima polimórfica sintetizada en el hígado y en el tejido adiposo, ampliamente distribuida en el organismo y encargada de hidrolizar algunos ésteres de colina como la procaína, ésteres alifáticos como el ácido acetilsalicílico, fármacos como la metilprednisolona, el mivacurium y la succinilcolina y drogas de uso y/o abuso como la heroína y la cocaína. Es codificada por el gen BCHE (OMIM 177400), habiéndose identificado más de 100 variantes, algunas no estudiadas plenamente, además de la forma más frecuente, llamada usual o silvestre. Diferentes polimorfismos del gen BCHE se han relacionado con la síntesis de enzimas con niveles variados de actividad catalítica. Las bases moleculares de algunas de esas variantes genéticas han sido reportadas, entre las que se encuentra las variantes Atípica (A), fluoruro-resistente del tipo 1 y 2 (F-1 y F-2), silente (S), Kalow (K), James (J) y Hammersmith (H). En este estudio, en un grupo de pacientes se aplicó el instrumento validado Lifetime Severity Index for Cocaine Use Disorder (LSI-C) para evaluar la gravedad del consumo de “cocaína” a lo largo de la vida. Además, se determinaron Polimorfismos de Nucleótido Simple (SNPs) en el gen BCHE conocidos como responsables de reacciones adversas en pacientes consumidores de “cocaína” mediante secuenciación del gen y se predijo el efecto delos SNPs sobre la función y la estructura de la proteína, mediante el uso de herramientas bio-informáticas. El instrumento LSI-C ofreció resultados en cuatro dimensiones: consumo a lo largo de la vida, consumo reciente, dependencia psicológica e intento de abandono del consumo. Los estudios de análisis molecular permitieron observar dos SNPs codificantes (cSNPs) no sinónimos en el 27.3% de la muestra, c.293A>G (p.Asp98Gly) y c.1699G>A (p.Ala567Thr), localizados en los exones 2 y 4, que corresponden, desde el punto de vista funcional, a la variante Atípica (A) [dbSNP: rs1799807] y a la variante Kalow (K) [dbSNP: rs1803274] de la enzima BChE, respectivamente. Los estudios de predicción In silico establecieron para el SNP p.Asp98Gly un carácter patogénico, mientras que para el SNP p.Ala567Thr, mostraron un comportamiento neutro. El análisis de los resultados permite proponer la existencia de una relación entre polimorfismos o variantes genéticas responsables de una baja actividad catalítica y/o baja concentración plasmática de la enzima BChE y algunas de las reacciones adversas ocurridas en pacientes consumidores de cocaína.

Molecular structure and function of the glycine receptor chloride channel

The glycine receptor chloride channel (GlyR) is a member of the nicotinic acetylcholine receptor family of ligand-gated ion channels. Functional receptors of this family comprise five subunits and are important targets for neuroactive drugs. The GlyR is best known for mediating inhibitory neurotransmission in the spinal cord and brain stem, although recent evidence suggests it may also have other physiological roles, including excitatory neurotransmission in embryonic neurons. To date, four alpha-subunits (alpha1 to alpha4) and one beta-subunit have been identified. The differential expression of subunits underlies a diversity in GlyR pharmacology. A developmental switch from alpha2 to alpha1beta is completed by around postnatal day 20 in the rat. The beta-subunit is responsible for anchoring GlyRs to the subsynaptic cytoskeleton via the cytoplasmic protein gephyrin. The last few years have seen a surge in interest in these receptors. Consequently, a wealth of information has recently emerged concerning Glyl? molecular structure and function. Most of the information has been obtained from homomeric alpha1 GlyRs, with the roles of the other subunits receiving relatively little attention. Heritable mutations to human GlyR genes give rise to a rare neurological disorder, hyperekplexia (or startle disease). Similar syndromes also occur in other species. A rapidly growing list of compounds has been shown to exert potent modulatory effects on this receptor. Since GlyRs are involved in motor reflex circuits of the spinal cord and provide inhibitory synapses onto pain sensory neurons, these agents may provide lead compounds for the development of muscle relaxant and peripheral analgesic drugs.

Inhibition of CYP1A2-mediated drug metabolism in vitro and in humans : With special emphasis on rofecoxib and other NSAIDs

The cytochrome P450 1A2 (CYP1A2) is one of the major metabolizing enzymes. The muscle relaxant tizanidine is a selective substrate of CYP1A2, and the non-steroidal anti-inflammatory drug (NSAID) rofecoxib was thought to modestly in-hibit it. Cases suggesting an interaction between tizanidine and rofecoxib had been reported, but the mechanism was unknown. Also other NSAIDs are often used in combination with muscle relaxants. The aims of this study were to investigate the effect of rofecoxib, several other NSAIDs and female sex steroids on CYP1A2 ac-tivity in vitro and in vivo, and to evaluate the predictability of in vivo inhibition based on in vitro data. In vitro, the effect of several NSAIDs, female sex steroids and model inhibitors on CYP1A2 activity was studied in human liver microsomes, without and with preincubation. In placebo controlled, cross-over studies healthy volunteers ingested a single dose of tizanidine after a pretreament with the inhibitor (rofecoxib, tolfenamic acid or celecoxib) or placebo. Plasma (and urine) concentrations of tizanidine and its metabolites were measured, and the pharmacodynamic effects were recorded. A caffeine test was also performed. In vitro, fluvoxamine, tolfenamic acid, mefenamic acid and rofecoxib potently in-hibited CYP1A2. Ethinylestradiol, celecoxib, desogestrel and zolmitriptan were moderate, and etodolac, ciprofloxacin, etoricoxib and gestodene were weak inhibi-tors of CYP1A2. At 100 µM, other tested NSAIDs and steroids inhibited CYP1A2 less than 35%. Rofecoxib was found to be a mechanism-based inhibitor of CYP1A2. In vivo, rofecoxib greatly increased the plasma concentrations (over ten-fold) and the pharmacodynamic effects of tizanidine. Also the metabolism of caf-feine was impaired by rofecoxib. Despite the relatively strong in vitro CYP1A2 inhibitory effects, tolfenamic acid and celecoxib did not have a significant effect on tizanidine and caffeine concentrations in humans. Competitive inhibition model and the free plasma concentration of the inhibitor predicted well the effect of fluvoxam-ine and the lack of effect of tolfenamic acid and celecoxib on tizanidine concentra-tions in humans, and mechanism-based inhibition model explained the effects of rofecoxib. However, the effects of ciprofloxacin and oral contraceptives were un-derestimated from the in vitro data. Rofecoxib is a potent mechanism-based inhibitor of CYP1A2 in vitro and in vivo. This mechanism may be involved in the adverse cardiovascular effects of rofecoxib. Tolfenamic acid and celecoxib seem to be safe in combination with tizanidine, but mefenamic acid might have some effect on tizanidine concentrations in vivo. Con-sidering the mechanism of inhibition, and using the free plasma concentration of the inhibitor, many but not all CYP1A2 interactions can be predicted from in vitro data.

The incidence of unacceptable movement with motor evoked potentials during craniotomy for aneurysm clipping.

OBJECTIVE: To review the experience at a single institution with motor evoked potential (MEP) monitoring during intracranial aneurysm surgery to determine the incidence of unacceptable movement. METHODS: Neurophysiology event logs and anesthetic records from 220 craniotomies for aneurysm clipping were reviewed for unacceptable patient movement or reason for cessation of MEPs. Muscle relaxants were not given after intubation. Transcranial MEPs were recorded from bilateral abductor hallucis and abductor pollicis muscles. MEP stimulus intensity was increased up to 500 V until evoked potential responses were detectable. RESULTS: Out of 220 patients, 7 (3.2%) exhibited unacceptable movement with MEP stimulation-2 had nociception-induced movement and 5 had excessive field movement. In all but one case, MEP monitoring could be resumed, yielding a 99.5% monitoring rate. CONCLUSIONS: With the anesthetic and monitoring regimen, the authors were able to record MEPs of the upper and lower extremities in all patients and found only 3.2% demonstrated unacceptable movement. With a suitable anesthetic technique, MEP monitoring in the upper and lower extremities appears to be feasible in most patients and should not be withheld because of concern for movement during neurovascular surgery.

Control of uncertain compartmental systems

Os sistemas compartimentais são frequentemente usados na modelação de diversos processos em várias áreas, tais como a biomedicina, ecologia, farmacocinética, entre outras. Na maioria das aplicações práticas, nomeadamente, aquelas que dizem respeito à administração de drogas a pacientes sujeitos a cirurgia, por exemplo, a presença de incertezas nos parâmetros do sistema ou no estado do sistema é muito comum. Ao longo dos últimos anos, a análise de sistemas compartimentais tem sido bastante desenvolvida na literatura. No entanto, a análise da sensibilidade da estabilidade destes sistemas na presença de incertezas tem recebido muito menos atenção. Nesta tese, consideramos uma lei de controlo por realimentação do estado com restrições de positividade e analisamos a sua robustez quando aplicada a sistemas compartimentais lineares e invariantes no tempo com incertezas nos parâmetros. Além disso, para sistemas lineares e invariantes no tempo com estado inicial desconhecido, combinamos esta lei de controlo com um observador do estado e a robustez da lei de controlo resultante também é analisada. O controlo do bloqueio neuromuscular por meio da infusão contínua de um relaxante muscular pode ser modelado como um sistema compartimental de três compartimentos e tem sido objecto de estudo por diversos grupos de investigação. Nesta tese, os nossos resultados são aplicados a este problema de controlo e são fornecidas estratégias para melhorar os resultados obtidos.

Sugammadex: su eficacia y seguridad en la reversión selectiva del vecuronio

Introducción: En 1979, con la monitorización del uso rutinario de los relajantes neuromusculares, se determinó incidencia en la relajación neuromuscular residual del 45%, con múltiples complicaciones respiratorias que incrementan la estancia hospitalaria. No es conocida la eficacia y seguridad del manejo del vecuronio y su reversión con el uso del sugammadex dentro del manejo rutinario de anestesia. Métodos: Revisión sistemática de artículos sobre el comportamiento del sugammadex cuando se realiza reversión para el efecto del vecuronio, por ser la primera droga que ha demostrado eficacia y seguridad frente a relajantes musculares no despolarizantes esteroideos, que ayuda a prevenir bloqueo residual en el posoperatorio. Resultados: Búsqueda en las bases de datos de EMBASE, EBSCO y MEDLINE y Pubmed (desde enero 2000-diciembre 2012), con palabras MeSH, sugammadex, vecuronium, binding reversal agents, neuromuscular blocking agents; artículos en idioma inglés de estudios clínicos controlados en pacientes humanos adultos en los cuales el sugammadex fue comparado con placebo u otro medicamento. Se aprecia disminución del tiempo de recuperación de la relajación neuromuscular en el bloqueo moderado con un rango de 1,5 a 2,3min con el sugammadex vs 18,9 a 66,2min con la neostigmine y en un bloqueo profundo desde 35,5-68,4min, con dosis de 0,5mgrs/kg de sugammadex hasta 1,4-1,7min con 8mgrs/kg. Discusión: Resultados favorables en el suministro de dosis mayores a 2mgrs/kg en pacientes que presentaban bloqueo neuromuscular moderado y mayores de 4mgrs/kg en bloqueo neuromuscular profundo. Existe necesidad de nuevos estudios clínicos que soporten estos hallazgos. Conclusión: La evidencia sugiere que sí existe una adecuada reversión de la relajación neuromuscular del vecuronio con el uso de sugammadex a 2mgrs/kg, con disminución importante del tiempo y mayor recuperación del paciente sin presencia de relajación residual.

Evaluación del Rocuronio Mediante Aceleromiografía en Pacientes con Sobrepeso u Obesidad

Introducción El rocuronio es un relajante muscular utilizado en la práctica anestésica diaria en la que la dosis depende del peso corporal. Se ha demostrado que en el paciente obeso se debe calcular en base a el peso ideal y no al peso real; sin embargo, no hay claridad de como esto modifica el tiempo de latencia y recuperación del medicamento en esta población. Metodología Se realizó un estudio observacional prospectivo para evaluar los resultados de la aceleromiografía en pacientes con sobrepeso u obesidad comparados con pacientes con IMC normal. Los desenlaces fueron tiempo de latencia, tiempo duración 25 y tiempo de recuperación de la función neuromuscular. Resultados Se incluyeron 40 pacientes por medio de muestreo por conveniencia con una relación de 1:1 según peso corporal. No hubo diferencias significativas en las condiciones de la población a diferencia de la clasificación de ASA y el IMC (p=0,03). En el tiempo de latencia no hubo diferencias significativas (p=0.31) ni en el tiempo duración 25, y al evaluar los tiempos de recuperación del bloqueo neuromuscular se encontró una diferencia significativa en los pacientes con sobrepeso (p=0.01). Ningún paciente requirió reversión farmacológica del rocuronio. Discusión Se puede afirmar que existe una disminución en la duración de acción del rocuronio en pacientes con IMC elevado, significativamente menor a la descrita en la literatura para las dosis aplicadas. La dosificación basada en peso ideal puede realmente ser insuficiente en el paciente con sobrepeso u obesidad para alcanzar la duración clínica de este medicamento.

The tof-guard neuromuscular transmission monitor and its use in horses

Quando da utilização de bloqueadores neuromusculares, já foi enfatizado na literatura médica humana, que é de vital imporância a monitoração do bloqueio neuromuscular e que estes agentes nunca devem ser utilizados sem a mesma. O objetivo deste estudo foi o de avaliar o uso do monitor da transmissão neuromuscular TOF-Guard em eqüinos. Para tanto, doze eqüinos foram separados aleatoriamente para receberem como bloqueadores neuromusculares o pancurônio ou o atracúrio. Todos os eqüinos foram pré-medicados com romifidina, induzidos com diazepam e quetamina e mantidos com halotano. Foi administrado o atracúrio ou o pancurônio, seguindo-se a apnéia e início da ventilação mecânica controlada. O tempo entre a administração do relaxante muscular e a obtenção de um bloqueio máximo (T1=0), o retorno do T1 para 25% e da razão do TOF para 0,7 e o tempo do retorno do T1 de 25 para 75% foram mensurados. Concluiu-se que é de grande importância a monitoração do bloqueio neuromuscular quando da utilização de um bloqueador neuromuscular não-despolarizante, uma vez que ela torna o ato anestésico e cirúrgico mais seguro, com a utilização de doses adequadas que inviabilizam a superficialização do bloqueio durante o procedimento cirúrgico. O monitor TOF-Guard mostrou ser uma boa opção para a monitoração do bloqueio neuromuscular em eqüinos.

Intraocular pressure evaluation of equines anesthetized with romifidine, tiletamine/zolazepam, halothane and vecuronium

O objetivo deste estudo foi o de avaliar uma associação anestésica com e sem a utilização de relaxante muscular não-despolarizante e seu efeito sobre a pressão intra-ocular de eqüinos. Também objetivou-se uma técnica anestésica sem efeitos adversos que possa ser utilizada em procedimentos e cirurgias oftálmicas nesta espécie animal. Para tanto, dezesseis eqüinos foram divididos aleatoriamente em dois grupos de oito animais cada. Os animais do grupo I foram pré-medicados com romifidina, induzidos com tiletamina/zolazepam e a anestesia foi mantida com halotano e vecurônio. Os animais do grupo II receberam a mesma associação anestésica, com exceção do vecurônio. No decorrer do experimento, a pressão intra-ocular, a pressão arterial e a freqüência cardíaca foram avaliadas em diferentes momentos. A associação anestésica composta pela romifidina, tiletamina/ zolazepam e halotano com e sem vecurônio não promoveu alterações estatisticamente significativas na pressão intra-ocular de eqüinos e o seu uso é exeqüível em procedimentos oftálmicos nesta espécie animal.

Parametria da associação do midazolam ou diazepam em cães pré-tratados pela atropina e tratados pela dexmedetomidina e quetamina

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the analgesic and antiedematogenic activities of Quassia amara bark extract

We evaluated the possible antiedematogenic, antinociceptive and/or sedative effects of four different extracts obtained from the bark of Quassia amara namely, 70% ethanol (70EtOH), 100% ethanol (100EtOH), dichloromethane (DCM) and hexane extracts (HEX). The oral administration (100, 250 and 500 mg/kg) of these extracts did not show significant effects in any experiment. However, when administered intraperitoneally, the HEX extract decreased the paw edema induced by carrageenan, showed antinociceptive effects on the hot-plate test and on acetic acid-induced writhing, and showed sedative effects on pentobarbital-induced sleep. Naloxone did not reverse the antinociceptive effect of this extract. In conclusion, although the mechanisms are uncertain, the results demonstrated that these effects are apparently related to sedative and muscle relaxant or psychomimetic activities of the HEX extract of the plant. (C) 2002 Elsevier B.V. Ireland Ltd. All rights reserved.

Two neighboring residues of loop A of the alpha1 subunit point towards the benzodiazepine binding site of GABAA receptors

Benzodiazepines are widely used drugs exerting sedative, anxiolytic, muscle relaxant, and anticonvulsant effects by acting through specific high affinity binding sites on some GABA(A) receptors. It is important to understand how these ligands are positioned in this binding site. We are especially interested here in the conformation of loop A of the alpha(1)beta(2)gamma(2) GABA(A) receptor containing a key residue for the interaction of benzodiazepines: alpha(1)H101. We describe a direct interaction of alpha(1)N102 with a diazepam- and an imidazobenzodiazepine-derivative. Our observations help to better understand the conformation of this region of the benzodiazepine pocket in GABA(A) receptor.

Proximity-accelerated chemical coupling reaction in the benzodiazepine-binding site of gamma-aminobutyric acid type A receptors: superposition of different allosteric modulators

Benzodiazepines are widely used drugs. They exert sedative/hypnotic, anxiolytic, muscle relaxant, and anticonvulsant effects and act through a specific high affinity binding site on the major inhibitory neurotransmitter receptor, the gamma-aminobutyric acid type A (GABA(A)) receptor. Ligands of the benzodiazepine-binding site are classified into three groups depending on their mode of action: positive and negative allosteric modulators and antagonists. To rationally design ligands of the benzodiazepine site in different isoforms of the GABA(A) receptor, we need to understand the relative positioning and overlap of modulators of different allosteric properties. To solve these questions, we used a proximity-accelerated irreversible chemical coupling reaction. GABA(A) receptor residues thought to reside in the benzodiazepine-binding site were individually mutated to cysteine and combined with a cysteine-reactive benzodiazepine site ligand. Direct apposition of reaction partners is expected to lead to a covalent reaction. We describe here such a reaction of predominantly alpha(1)H101C and also three other mutants (alpha(1)G157C, alpha(1)V202C, and alpha(1)V211C) with an Imid-NCS derivative in which a reactive isothiocyanate group (-NCS) replaces the azide group (-N(3)) in the partial negative allosteric modulator Ro15-4513. Our results show four contact points of imidazobenzodiazepines with the receptor, alpha(1)H101C being shared by classical benzodiazepines. Taken together with previous data, a similar orientation of these ligands within the benzodiazepine-binding pocket may be proposed.