“Off-label” use occurs when a medication is prescribed for non-approved purposes. This case study explored physician experiences with prescribing gabapentin off-label. Semi-structured interviews with 10 specialists in the Greater Toronto Area provided data that were analyzed using qualitative content analysis. Specialists described prescribing gabapentin off-label as common practice and few expressed concerns about its safety. Knowledge from various interconnected sources influenced off-label prescribing decisions. These included: social knowledge, scientific knowledge, knowledge of the drug, knowledge of the patient, and experiential knowledge. Findings were similar to previous studies examining physician prescribing behaviour. Furthermore, lack of provincial-government reimbursement for off-label uses of gabapentin (knowledge of drug coverage) was a significant barrier to prescribing. Off-label prescribing differs from other types of prescribing since there is often a lack of scientific evidence for off-label uses. The complexities of the off-label prescribing process and the degree of importance between the various influences require further exploration.

“Off-label” use occurs when a medication is prescribed for non-approved purposes. This case study explored physician experiences with prescribing gabapentin off-label. Semi-structured interviews with 10 specialists in the Greater Toronto Area provided data that were analyzed using qualitative content analysis. Specialists described prescribing gabapentin off-label as common practice and few expressed concerns about its safety. Knowledge from various interconnected sources influenced off-label prescribing decisions. These included: social knowledge, scientific knowledge, knowledge of the drug, knowledge of the patient, and experiential knowledge. Findings were similar to previous studies examining physician prescribing behaviour. Furthermore, lack of provincial-government reimbursement for off-label uses of gabapentin (knowledge of drug coverage) was a significant barrier to prescribing. Off-label prescribing differs from other types of prescribing since there is often a lack of scientific evidence for off-label uses. The complexities of the off-label prescribing process and the degree of importance between the various influences require further exploration.

Intractable hiccups are not common in the general population or in the palliative care population but can adversely impact quality of life and cause other complications such as weight loss and sleep disturbance. Many treatments have been proposed for intractable hiccups, but there is little consensus regarding treatment in the medical literature. This is partly because hiccups are relatively uncommon and many of the proposed treatments are unproven or have long-term side effects. Pharmacologic treatments rather than home remedies or surgical treatments are more appropriate for the palliative care patient. Gabapentin is a promising medication for the treatment of intractable hiccups for its safety, lack of serious side effects, and rapid onset of action. Further research is indicated to determine whether gabapentin is consistently effective.

Epilepsy has been previously attributed to either increased excitation or decreased inhibition. With this closed frame of mind, modern medicine has been unable to develop a permanent treatment against the mechanisms of epilepsy. In order to treat patients with intractable seizures, especially those caused by developmental malformations, it is essential to understand the entirety of mechanisms that could possibly play a role in the abnormal cortical function. One such developmental malformation is known as polymicrogyria. Epileptogenesis occurs in an area laterally adjacent to this malformation known as the paramicrogyral region (PMR). Past studies have narrowed down the potential cause of this increased network excitation to a certain type of inhibitory interneuron, the somatostatin (SS) interneuron. Additionally, previous studies have shown an increase in the mGlu5 receptor on this interneurons in the PMR region only and not in control tissue, meaning that targeting these receptors as treatment will not affect normal functioning tissue. These results lead to our hypothesis: blockade of the mGluRs will decrease the 2 activity of SS interneurons and thereby prevent the generation of epileptiform activity and increased SS output in malformed cortex. Utilizing the freeze-lesion model for microgyria in transgenic mice expressing Channelrhodopsin optogenetic channels in SS interneurons, we assessed the contribution of these SS interneurons in four different animal groups: control or PMR treated with either Gabapentin, a current AED (antiepileptic drug), or MTEP, an mGlu5 receptor antagonist. We tested the effects of these two drugs on SS interneuron output to determine whether they decrease the over activation in the PMR that has been previously studied. The following study revealed no correlation between Gabapentin-treated animals and a decrease in epileptiform activity. Additionally, no significant difference was seen between the MTEP-treated groups in the protocols that were measured.

A utilização de adjuvantes como gabapentina e amitriptilina por via sistêmica é uma ótima opção no tratamento analgésico de síndromes dolorosas crônicas que culminam com hiperalgesia e alodinia, com baixa incidência de efeitos colaterais. Entretanto, os efeitos do emprego destes fármacos em cães ainda são pouco conhecidos, bem como sua real aplicação, pois faltam estudos clínicos nesta espécie. Portanto, este estudo teve o intuito de avaliar a ação analgésica da administração de isolada de gabapentina ou amitriptilina em cães portadores de dor crônica de qualquer etiologia que não oncollógica. Avaliou-se o efeito analgésico através da escala numérica verbal (ENV), questionário de qualidade de vida e testes para verificação de alodinia. Foram também avaliados os valores do hemograma completo, funções hepática e renal dos animais incluídos no estudo antes e após o tratamento, afim de que a segurança dos fármacos seja verificada.Foram dosados níveis séricos de TNF-α e IL-6 para comparação dos valores antes e após a terapia. Animais que necessitaram de resgate analgésico receberam dipirina 25 mg/kg. Foram utilizados 18 animais provenientes do Ambulatório de Dor e Cuidados Paliativos do Hospital Veterinário da Universidade de São Paulo. Estes animais foram distribuídos em 2grupos de forma aleatória, com 9 animais em cada grupo. Os animais participantes do presente estudo receberagabapentina na dose de 10 mg/kg a cada 12 horas, ou amitriptilina 1 mg/kga cada 24 horas pela via oral.Os retornos foram realizados semanalmente, avaliando-se valores da ENV, qualidade de vida e alodinia. Os resultados foram analisados estatisticamente pelo teste de Wilcoxon para dados não paramétricos. Com base nos resultados obtidos, pôde-se concluir que o uso isolado da gabapentina e da amitriptilina promovemelhora na qualidade de vida e redução dos escores na ENV em cães portadores de dor crônica neuropática, apesar de demonstrarem resultados ainda melhores como parte de um protocolo de analgesiamultimodal. A amitriptilina demonstrou-se superior, pois os componentes de seu grupo não necessitaram de resgate e obtiveram maior redução de escores de dor na ENV e alodinia e melhores índices de qualidade de vida. Os animais pertencentes ao grupo da gabapentina não apresentaram melhora significativa nos parâmetros observados. Não foram observados efeitos adversos relacionados durante o período do estudo. / The use of adjuvants such as amitriptyline and gabapentin systemically is a great option in analgesic treatment of chronic pain syndromes that culminate with hyperalgesia and allodynia, with a low incidence of side effects. However, the employment effects of these drugs in dogs are still poorly understood, and their actual implementation, because clinical trials are lacking in this species. Therefore, this study aimed to evaluate the analgesic effect of single administration of gabapentin or amitriptyline in dogs with chronic pain of any etiology but cancer. The analgesic effect was evaluadted by the verbal numeric scale (VNS), quality of life questionnaire and tests to check allodynia. Was also evaluated the values of blood count, liver and renal function of animals included in the study before and after treatment, in order to verify the safety of the drugs. Serum levels of TNF-α and IL-6 were measured for comparison of values before and after therapy.Animalswho required analgesic rescued recevied 25 mg/kg of dipyrone or it combined with 2 mg/kg of tramadol. Eighteen animals provenient from the Clinic of Pain and Palliative Care of the Veterinary Hospital of the University of São Paulo were used for this study. There animals were radomly divided into two groups with nine animals per group.The animals in the present study received orally 10 mg/kg of gabapentin every 12 hours. The animals retornedeveryweek in order to evaluate the VNS values ,quality of life and allodynia. The results were statistically analyzed by the Wilcoxon test for nonparametric data and ANOVA for parametric data. In the VNS avaliation, no statistical significance between times or between groups were observed. There was a significant decrease in values of quality of life in two groups, between moment one and four, with p 0.05, but not between the two groups.Regarding the assessment of allodynia, only the amitriptyline group showed statistical significance, with p 0.05.Significance was not observed when comparing the two groups with regard to allodynia. There were no significant changes in parameters related to blood count, renal and hepatic function when compared to the data obtained before and after treatment with the study drugs.Based on these results, we concluded that adjuvant drugs used on this study promoted good analgesia for dogs with chronic non-oncologic pain, amitriptyline at a dose of 1 mg / kg demonstrated analgesic efficacy slightly superior to gabapentin at a dose of 10 mg / kg. No adverse effects related to physiological parameters were observed during the study period.

A utilização de adjuvantes como gabapentina e amitriptilina por via sistêmica é uma ótima opção no tratamento analgésico de síndromes dolorosas crônicas que culminam com hiperalgesia e alodinia, com baixa incidência de efeitos colaterais. Entretanto, os efeitos do emprego destes fármacos em cães ainda são pouco conhecidos, bem como sua real aplicação, pois faltam estudos clínicos nesta espécie. Portanto, este estudo teve o intuito de avaliar a ação analgésica da administração de isolada de gabapentina ou amitriptilina em cães portadores de dor crônica de qualquer etiologia que não oncollógica. Avaliou-se o efeito analgésico através da escala numérica verbal (ENV), questionário de qualidade de vida e testes para verificação de alodinia. Foram também avaliados os valores do hemograma completo, funções hepática e renal dos animais incluídos no estudo antes e após o tratamento, afim de que a segurança dos fármacos seja verificada.Foram dosados níveis séricos de TNF-α e IL-6 para comparação dos valores antes e após a terapia. Animais que necessitaram de resgate analgésico receberam dipirina 25 mg/kg. Foram utilizados 18 animais provenientes do Ambulatório de Dor e Cuidados Paliativos do Hospital Veterinário da Universidade de São Paulo. Estes animais foram distribuídos em 2grupos de forma aleatória, com 9 animais em cada grupo. Os animais participantes do presente estudo receberagabapentina na dose de 10 mg/kg a cada 12 horas, ou amitriptilina 1 mg/kga cada 24 horas pela via oral.Os retornos foram realizados semanalmente, avaliando-se valores da ENV, qualidade de vida e alodinia. Os resultados foram analisados estatisticamente pelo teste de Wilcoxon para dados não paramétricos. Com base nos resultados obtidos, pôde-se concluir que o uso isolado da gabapentina e da amitriptilina promovemelhora na qualidade de vida e redução dos escores na ENV em cães portadores de dor crônica neuropática, apesar de demonstrarem resultados ainda melhores como parte de um protocolo de analgesiamultimodal. A amitriptilina demonstrou-se superior, pois os componentes de seu grupo não necessitaram de resgate e obtiveram maior redução de escores de dor na ENV e alodinia e melhores índices de qualidade de vida. Os animais pertencentes ao grupo da gabapentina não apresentaram melhora significativa nos parâmetros observados. Não foram observados efeitos adversos relacionados durante o período do estudo. / The use of adjuvants such as amitriptyline and gabapentin systemically is a great option in analgesic treatment of chronic pain syndromes that culminate with hyperalgesia and allodynia, with a low incidence of side effects. However, the employment effects of these drugs in dogs are still poorly understood, and their actual implementation, because clinical trials are lacking in this species. Therefore, this study aimed to evaluate the analgesic effect of single administration of gabapentin or amitriptyline in dogs with chronic pain of any etiology but cancer. The analgesic effect was evaluadted by the verbal numeric scale (VNS), quality of life questionnaire and tests to check allodynia. Was also evaluated the values of blood count, liver and renal function of animals included in the study before and after treatment, in order to verify the safety of the drugs. Serum levels of TNF-α and IL-6 were measured for comparison of values before and after therapy.Animalswho required analgesic rescued recevied 25 mg/kg of dipyrone or it combined with 2 mg/kg of tramadol. Eighteen animals provenient from the Clinic of Pain and Palliative Care of the Veterinary Hospital of the University of São Paulo were used for this study. There animals were radomly divided into two groups with nine animals per group.The animals in the present study received orally 10 mg/kg of gabapentin every 12 hours. The animals retornedeveryweek in order to evaluate the VNS values ,quality of life and allodynia. The results were statistically analyzed by the Wilcoxon test for nonparametric data and ANOVA for parametric data. In the VNS avaliation, no statistical significance between times or between groups were observed. There was a significant decrease in values of quality of life in two groups, between moment one and four, with p 0.05, but not between the two groups.Regarding the assessment of allodynia, only the amitriptyline group showed statistical significance, with p 0.05.Significance was not observed when comparing the two groups with regard to allodynia. There were no significant changes in parameters related to blood count, renal and hepatic function when compared to the data obtained before and after treatment with the study drugs.Based on these results, we concluded that adjuvant drugs used on this study promoted good analgesia for dogs with chronic non-oncologic pain, amitriptyline at a dose of 1 mg / kg demonstrated analgesic efficacy slightly superior to gabapentin at a dose of 10 mg / kg. No adverse effects related to physiological parameters were observed during the study period.

Itch/pruritus can be very distressing in palliative care population and often is difficult to treat. Conventional antihistamines lack efficacy. Cutaneous and central pathogenesis of itch is extremely complex and unclear, making its treatment challenging. Neuronal mechanisms have been identified in the pathophysiology of itch hence providing a myriad of therapeutic options. It has been established that pruritus and pain neuronal pathway interact with each other, hence neuropathic analgesics like gabapentin has shown to be efficacious antipruritic therapeutic option. Gabapentin impedes transmitting nociceptive sensations to brain, thus also suppressing pruritus. Gabapentin is safe and found to be effective in uremic pruritus, cancer/hematologic causes, opiod-induced itch, brachioradial pruritis, burns pruritus, and pruritus of unknown origin. Further research is required in this area to establish whether gabapentin is consistently effective.

Itch/pruritus can be very distressing in palliative care population and often is difficult to treat. Conventional antihistamines lack efficacy. Cutaneous and central pathogenesis of itch is extremely complex and unclear, making its treatment challenging. Neuronal mechanisms have been identified in the pathophysiology of itch hence providing a myriad of therapeutic options. It has been established that pruritus and pain neuronal pathway interact with each other, hence neuropathic analgesics like gabapentin has shown to be efficacious antipruritic therapeutic option. Gabapentin impedes transmitting nociceptive sensations to brain, thus also suppressing pruritus. Gabapentin is safe and found to be effective in uremic pruritus, cancer/hematologic causes, opiod-induced itch, brachioradial pruritis, burns pruritus, and pruritus of unknown origin. Further research is required in this area to establish whether gabapentin is consistently effective.

Background Gabapentinoids (gabapentin and pregabalin), a class of FDA-approved antiepileptic medications with expanded indications for certain neuropathic pain conditions, have been prescribed off-label for almost all types of pain in the US opioid epidemic. Methods We used IBM® MarketScan® Research Databases (2015-2018) and collected primary data. In Aim 1, we described the geographic variation in gabapentinoids and opioids for pain by US state and metropolitan statistical area (MSA). In Aim 2, we implemented a controlled multiple baseline interrupted time series analysis and assessed the impact of including gabapentin in states’ prescription drug monitoring programs (PDMP) and listing gabapentin as a Schedule V controlled substance. In Aim 3, we developed an algorithm to identify potential gabapentin misuse and/or abuse in administrative claims data. Results The pattern of the geographic variation in gabapentinoids was similar to that of opioids across states and MSAs. Including gabapentin in PDMPs and Schedule V controlled ABSTRACT viii substance classification were effective in curbing the growth of gabapentin use and reducing opioid-related adverse events. Our algorithm identified approximately one in six patients with gabapentin use as having potentially misused and/or abused gabapentin. Multiple comorbidities and drug use were associated with gabapentin misuse and/or abuse. Conclusions Gabapentinoids may have been widely used as alternative or adjuvant analgesics to opioids for pain across the US. Policy makers should consider including gabapentin in proactive PDMPs and scheduling of gabapentin. Monitoring requirements and individualized safety measures should be put in place for patients who potentially misuse and/or abuse gabapentin.

The mammalian central nervous system maintains a delicate balance between neuronal excitation and inhibition. Conventional synaptic inhibition is mediated through the transient activity of postsynaptic γ-aminobutyric acid (GABA) at type A GABA (GABAA) receptors. A subset of GABAA receptors is also located outside of inhibitory synapses. These extrasynaptic receptors generate a tonic inhibitory conductance in response to low concentrations of extracellular GABA. Tonic inhibition broadly suppresses neuronal activity and regulates many vital processes such as sleep, consciousness and memory formation. This thesis examines the physiological effects of tonic inhibition at the cellular level and in the behaving animal. This thesis also explores whether gabapentin, a commonly used sedative, anxiolytic, and analgesic drug, enhances tonic GABAergic inhibition. I hypothesize that: (1) tonic GABAA receptor activity reduces the intrinsic excitability of neurons; (2) the activity of tonically active GABAA receptors in spinal pain pathways attenuates nociception; and (3) tonic inhibition can be upregulated by gabapentin. The results show that a tonic inhibitory current generated by α5 subunit-containing GABAA (α5GABAA) receptors reduces the excitability of hippocampal pyramidal neurons excitability by increasing the rheobase, but does not change the gain of action potential firing. A similar shunting inhibition is present in spinal cord lamina II neurons that is generated by δ subunit-containing GABAA receptors. The activity of these receptors in spinal nociceptive pathways reduces acute thermal nociception and may constrain central sensitization in a behavioural model of persistent pain. Finally, gabapentin increases a tonic inhibitory current in cultured hippocampal neurons independent from changes in the expression of α5GABAA receptors or in the concentration of GABAA receptor ligands. The results of this thesis demonstrate that tonically active GABAA receptors play an important role in the regulation of neuronal activity and nociception, and that tonic inhibition represents a novel target of therapeutic drugs.