Posttraumatic stress disorder (PTSD) is classified as an anxiety disorder and the characteristic symptoms (re-experiencing, avoidance as well as numbing of general responsiveness and hyperarousal) of this disorder develop in response to a traumatic event. The disorder is characterised by hypothalamic-pituitary-adrenal (HPA) axis abnormalities linked with changes in cortisol moreover, the hippocampus and cortex also play a role in the neurobiology. With regard to the neurochemistry of this disorder it is known that gamma amino butyric acid (GABA) is involved however, the precise role of GABA in PTSD and how stress changes GABA concentrations in the brain are still not fully understood. Another aspect regarding PTSD that has not been clearly defined is the treatment of PTSD. Classic anxiolytics such as diazepam is expected to relieve the anxiety linked with PTSD. Studies with this group of drugs have however not produced the concrete evidence needed to establish it as a treatment of choice for PTSD and subsequently other classes of drugs have been investigated as possible treatment options for PTSD. Among these is lamotrigine, which in a clinical study was found to be effective in alleviating symptoms of PTSD. Moreover, a possible pharmacokinetic-pharmacodynamic relationship for each of these drugs has also not been elucidated. In order to elude on some of these uncertainties, an animal model of PTSD, time dependent sensitisation (TDS), was used. GABA levels in the rat hippocampus and frontal cortex were determined at two different time intervals following the TDS procedure (1 day and 7 days post re-stress). High performance liquid chromatography (HPLC) with electrochemical (EC) detection was used to determine gamma amino butyric acid (GABA) concentrations. To investigate the possible anxiolytic effects of diazepam and lamotrigine in this model, as well as a possible pharmacokinetic-pharmacodynamic relationship for each drug, pharmacokinetic profiles for both drugs were established in order to find the times of peak and trough levels of each drug. Blood samples were collected at different time intervals after drug administration either from the tail vein of rats (lamotrigine) or directly from the heart (diazepam). Subsequently, drug concentrations at each time interval were determined by means of HPLC with ultraviolet (UV) detection. The behaviour of rats was analysed using the elevated plus-maze (EPM) at peak or trough concentrations of the drugs and this was performed after either acute administration of the drug, or after a 14 day chronic treatment regime. GABA levels in the hippocampus were not found to change statistically significantly in response to stress at either 1 day or 7 days post re-stress. In the frontal cortex, however, GABA levels increased in response to stress at 1 day post re-stress, with a statistically insignificant, but strong trend towards an increase, at 7 days post re-stress. With regard to the pharmacokinetic profiles, the peak concentration of diazepam was found to occur at 60 minutes, with lamotrigine's peak at 120 minutes. The behavioural studies indicated that acute treatment with diazepam 3 mg/kg resulted in a statistically significant increase in both ratio open arm entries and ratio time spent in the open arms at peak level of the drug. After acute treatment with diazepam 3 mg/kg a statistically significant decrease in ratio time spent in open arms was also found when the ratio time spent in open arms at peak level of the drug and the ratio time spent in open arms at trough level of the drug was compared. In response to chronic treatment with diazepam 3 mg/kg for 14 days, test animals exhibited an increase in the ratio open arm entries at trough level of the drug, with a statistically insignificant yet definite trend towards an increase at peak level. Acute treatment with lamotrigine 10 mg/kg resulted in no statistically significant change in EPM parameters. In response to chronic treatment, however, a statistically significant increase was found in ratio time spent in open arms at peak level of the drug, with a statistically insignificant trend towards an increase at trough level. From the results of this study, we may therefore conclude that GABA-levels in the brain are definitely affected, but in different ways, following TDS-stress. A pharmacokinetic-pharmacodynamic relationship between the drugs' levels and aversive behaviour could also be established. Furthermore it appears that more sustained anxiolytic effects are evident following chronic treatment with both drugs than with acute administration of these drugs. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2006

A lamotrigina é um fármaco relativamente novo que tem se mostrado útil no tratamento de diferentes crises epilépticas. Este fármaco encontra-se no mercado na forma de comprimidos e, apesar de seu amplo uso na terapêutica, não há descrição de métodos analíticos em códigos oficiais para o controle de qualidade da lamotrigina em sua forma farmacêutica. Estudos de estabilidade não foram encontrados na literatura científica, apenas dados fornecidos pela indústria. No FDA (2006) estão descritas as condições para o teste de dissolução dos comprimidos de lamotrigina, mas não há relatos sobre a forma de quantificação dos mesmos. Desta forma, o presente trabalho teve como objetivos o desenvolvimento e validação de métodos analíticos qualitativos e quantitativos, realização de estudo preliminar de estabilidade e o desenvolvimento e validação de método de dissolução para o controle de qualidade da lamotrigina em comprimidos.A caracterização da substância química de referência foi realizada através de calorimetria diferencial exploratória (DSC) e espectrofotometria na região do infravermelho (IV). A cromatografia em camada delgada (CCD), espectrofotometria de absorção no ultravioleta (UV) e cromatografia líquida de alta eficiência (CLAE) foram utilizadas para identificação da lamotrigina em comprimidos. Para a quantificação dos comprimidos, foram utilizadas a espectrofotometria de absorção no ultravioleta (UV) e cromatografia líquida de alta eficiência (CLAE). O estudo preliminar de estabilidade térmica foi realizado submetendo-se as amostras ao calor seco de 80ºC. A fotoestabilidade foi avaliada em soluções de lamotrigina armazenadas em câmara de luz a 254 nm por um período de até quinze dias, demonstrando que o fármaco é sensível à luz. As amostras também foram submetidas à hidrólise ácida por um período de 54 horas, observando-se decaimento no teor do fármaco. Foi desenvolvido e validado um método de dissolução simples e rápido para o controle de qualidade dos comprimidos de lamotrigina. / Lamotrigine is a relative new antiepileptic drug that seems useful in the treatment of different seizures. Lamotrigine can be found in the market in tablets. Despite being used in therapeutics, methods for quality control of lamotrigine in tablets are not available in the official codes. Stability studies were just informed by the producer. FDA (2006) described the conditions of dissolution test to lamotrigine in tablets, but there is nothing about the quantification method. In this way, the aim of this work was the development and validation of analytical methods, preliminary study of stability and the development and validation of a dissolution method to quality control of lamotrigine in tablets. The characterization of the reference standard was carried out by differential scanning calorimetry (DSC) and infrared spectroscopy (IR). Thin-layer chromatography (CCD), ultraviolet spectroscopy (UV) and high performance liquid chromatography (HPLC) was performed to lamotrigine qualitative analysis. UV and HPLC were performed to lamotrigine quantitative analysis. The sample solutions were submitted under UV-light at 254 nm during 15 days, showing degradation and decrease in the labeled amount. Thermal degradation was carried by dry heat at 80°C in solid powder. The solution samples was also submitted to acid condition with HCL 1 M during 54 hours. Rapid and simple dissolution method to routine quality control of lamotrigine was developed and validated.

A lamotrigina é um fármaco relativamente novo que tem se mostrado útil no tratamento de diferentes crises epilépticas. Este fármaco encontra-se no mercado na forma de comprimidos e, apesar de seu amplo uso na terapêutica, não há descrição de métodos analíticos em códigos oficiais para o controle de qualidade da lamotrigina em sua forma farmacêutica. Estudos de estabilidade não foram encontrados na literatura científica, apenas dados fornecidos pela indústria. No FDA (2006) estão descritas as condições para o teste de dissolução dos comprimidos de lamotrigina, mas não há relatos sobre a forma de quantificação dos mesmos. Desta forma, o presente trabalho teve como objetivos o desenvolvimento e validação de métodos analíticos qualitativos e quantitativos, realização de estudo preliminar de estabilidade e o desenvolvimento e validação de método de dissolução para o controle de qualidade da lamotrigina em comprimidos.A caracterização da substância química de referência foi realizada através de calorimetria diferencial exploratória (DSC) e espectrofotometria na região do infravermelho (IV). A cromatografia em camada delgada (CCD), espectrofotometria de absorção no ultravioleta (UV) e cromatografia líquida de alta eficiência (CLAE) foram utilizadas para identificação da lamotrigina em comprimidos. Para a quantificação dos comprimidos, foram utilizadas a espectrofotometria de absorção no ultravioleta (UV) e cromatografia líquida de alta eficiência (CLAE). O estudo preliminar de estabilidade térmica foi realizado submetendo-se as amostras ao calor seco de 80ºC. A fotoestabilidade foi avaliada em soluções de lamotrigina armazenadas em câmara de luz a 254 nm por um período de até quinze dias, demonstrando que o fármaco é sensível à luz. As amostras também foram submetidas à hidrólise ácida por um período de 54 horas, observando-se decaimento no teor do fármaco. Foi desenvolvido e validado um método de dissolução simples e rápido para o controle de qualidade dos comprimidos de lamotrigina. / Lamotrigine is a relative new antiepileptic drug that seems useful in the treatment of different seizures. Lamotrigine can be found in the market in tablets. Despite being used in therapeutics, methods for quality control of lamotrigine in tablets are not available in the official codes. Stability studies were just informed by the producer. FDA (2006) described the conditions of dissolution test to lamotrigine in tablets, but there is nothing about the quantification method. In this way, the aim of this work was the development and validation of analytical methods, preliminary study of stability and the development and validation of a dissolution method to quality control of lamotrigine in tablets. The characterization of the reference standard was carried out by differential scanning calorimetry (DSC) and infrared spectroscopy (IR). Thin-layer chromatography (CCD), ultraviolet spectroscopy (UV) and high performance liquid chromatography (HPLC) was performed to lamotrigine qualitative analysis. UV and HPLC were performed to lamotrigine quantitative analysis. The sample solutions were submitted under UV-light at 254 nm during 15 days, showing degradation and decrease in the labeled amount. Thermal degradation was carried by dry heat at 80°C in solid powder. The solution samples was also submitted to acid condition with HCL 1 M during 54 hours. Rapid and simple dissolution method to routine quality control of lamotrigine was developed and validated.

A lamotrigina (LTG) é um fármaco pertencente à classe das feniltriazinas utilizado no tratamento de crises epilépticas generalizadas e focais e no tratamento adjunto da epilepsia refratária. Devido à alta variabilidade interindividual, às interações medicamentosas e aos efeitos adversos apresentados durante a administração da LTG, a monitorização terapêutica nos pacientes que fazem uso deste fármaco é necessária para ajuste de dose individual e evitar os efeitos adversos. Assim, o objetivo deste trabalho foi a avaliação de duas técnicas de microextração: a microextração em fase líquida com fibras ocas (HF-LPME) e a microextração líquido-líquido dispersiva (DLLME) para análise da lamotrigina em amostras de plasma de pacientes epilépticos. Primeiramente foram definidas as condições eletroforéticas: foi utilizado um capilar de sílica fundida de 75 ?m de diâmetro interno e 50 cm de comprimento efetivo. O eletrólito de corrida (BGE) foi composto por ácido 2-morfolinoetanosulfônico (MES), na concentração de 130 mmol L-1 e pH 5,0. As análises foram realizadas à temperatura de 20°C e tensão de 15 kV. A amostra foi injetada hidrodinamicamente (0,5 psi por 10 s) e a detecção foi feita em 214 nm. Nestas condições a LTG e o padrão interno (PI), lidocaína, puderam ser analisados em menos de 7 minutos. A HF-LPME foi avaliada no modo de 3 fases, usando 500 ?L de plasma e 3,5 mL de solução fosfato de sódio 50 mmol L-1 pH 9,0 como fase doadora. O solvente utilizado para impregnar a fibra foi o 1-octanol. Como fase aceptora foram utilizados 60 ?L de solução de ácido clorídrico pH 4,0. Para avaliação da DLLME, foi necessária uma etapa de pré-tratamento da amostra (500 ?L de plasma) com 1 mL de acetonitrila. Após isto, 1,3 mL do sobrenadante foram adicionados a 4 mL de solução fosfato de sódio 50 mmol L-1 pH 9,0 e 120 ?L de clorofórmio (solvente extrator) foram injetados nesta amostra aquosa e 165 ?L de fase sedimentada foram recuperados. As características de desempenho analítico para ambos os métodos foram avaliadas, sendo obtida linearidade na faixa de concentração plasmática de 1-20 ?g/mL e limite inferior de quantificação (LIQ) de 1 ?g mL-1. Os ensaios de precisão e exatidão apresentaram valores de acordo com os guias oficiais. Além disso, os métodos foram seletivos, não apresentaram efeito residual e as amostras foram estáveis. Os valores de recuperação foram de 54,3 e 23% para HF-LPME e DLLME, respectivamente. Os métodos validados foram aplicados com sucesso em amostras de plasma de pacientes epilépticos em tratamento com a LTG. Além disso, as duas técnicas foram comparadas e a HF-LPME apresentou vantagens em relação à DLLME, mostrando ser uma técnica promissora para análise de matrizes complexas, com reduzido consumo de solvente orgânico e possibilidade de automação. / Lamotrigine (LTG) is an antiepileptic drug, which belongs to the class of phenyltriazine that can be used in the treatment of new-onset and refractory epilepsy. Due to its high interindividual variability, drug interactions and the adverse effects presented during the LTG administration, therapeutic drug monitoring is very important to dose adjustment and to avoid toxicity effects. Thus, the goal of this study was to develop and validate two microextraction techniques: the hollow fiber liquid-phase microextraction (HF-LPME) and the dispersive liquid-liquid microextraction (DLLME) to analyze LTG in plasma samples of epileptic patients. First of all, the eletroforetic conditions were optimized. A fused-silica uncoated capillary with 75 ?m internal diameter, and 50 cm effective length was used. The 2-(N-morpholino)ethanesulfonic acid (MES) 130 mmol L-1 pH 5.0 was chosen as background electrolyte (BGE). The temperature and the voltage were kept constant at 20°C and 15 kV respectively. For sample injection, hydrodynamic injection mode was used, with a pressure of 0.5 psi applied for 10 s. The wavelength was set at 214 nm. Under final conditions, LTG and the internal standard (IS) lidocaine were analyzed in less than 7 minutes. HF-LPME was evaluated in the three phase mode. The analyte was extracted from 4.0 mL of a basic donor phase (composed of 500 ?L of plasma and 3.5 mL of sodium phosphate solution 50 mmol L-1 pH 9.0) into an organic phase composed of 1-octanol immobilized in the pores of the hollow fiber, and further into an acidic acceptor phase (hydrochloric acid solution pH 4.0) placed in the lumen of the fiber. To evaluate DLLME, the plasma samples were pretreated to remove the proteins, and 500 ?L of plasma sample was mixed with 1 mL of acetonitrile. After that, 1,3 mL of the upper layer was added to 4 mL of sodium phosphate solution 50 mmol L-1 pH 9.0, and 120 ?L of chloroform (extracting solvent) was rapidly injected in the aqueous sample and 165 ?L of the sedimented phase was collected. Under the optimized conditions, both methods were linear over the plasmatic concentration range of 1.0-20.0 ?g mL-1 and the lower limit of quantification (LLOQ) was 1.0 ?g mL-1. Both methods showed good precision, accuracy, selectivity to LTG, with no carryover and the samples were stable under the studied conditions. The recovery were 54,3 and 23% to HF-LPME and DLLME respectively. The validated methods were successfully applied for the quantification of LTG in plasma samples of epileptic patients. The techniques were compared and HF-LPME was more advantageous for being more suitable to analysis of complex matrices using small amount of organic solvent, and also can be automated.

A lamotrigina (LTG) é um fármaco pertencente à classe das feniltriazinas utilizado no tratamento de crises epilépticas generalizadas e focais e no tratamento adjunto da epilepsia refratária. Devido à alta variabilidade interindividual, às interações medicamentosas e aos efeitos adversos apresentados durante a administração da LTG, a monitorização terapêutica nos pacientes que fazem uso deste fármaco é necessária para ajuste de dose individual e evitar os efeitos adversos. Assim, o objetivo deste trabalho foi a avaliação de duas técnicas de microextração: a microextração em fase líquida com fibras ocas (HF-LPME) e a microextração líquido-líquido dispersiva (DLLME) para análise da lamotrigina em amostras de plasma de pacientes epilépticos. Primeiramente foram definidas as condições eletroforéticas: foi utilizado um capilar de sílica fundida de 75 ?m de diâmetro interno e 50 cm de comprimento efetivo. O eletrólito de corrida (BGE) foi composto por ácido 2-morfolinoetanosulfônico (MES), na concentração de 130 mmol L-1 e pH 5,0. As análises foram realizadas à temperatura de 20°C e tensão de 15 kV. A amostra foi injetada hidrodinamicamente (0,5 psi por 10 s) e a detecção foi feita em 214 nm. Nestas condições a LTG e o padrão interno (PI), lidocaína, puderam ser analisados em menos de 7 minutos. A HF-LPME foi avaliada no modo de 3 fases, usando 500 ?L de plasma e 3,5 mL de solução fosfato de sódio 50 mmol L-1 pH 9,0 como fase doadora. O solvente utilizado para impregnar a fibra foi o 1-octanol. Como fase aceptora foram utilizados 60 ?L de solução de ácido clorídrico pH 4,0. Para avaliação da DLLME, foi necessária uma etapa de pré-tratamento da amostra (500 ?L de plasma) com 1 mL de acetonitrila. Após isto, 1,3 mL do sobrenadante foram adicionados a 4 mL de solução fosfato de sódio 50 mmol L-1 pH 9,0 e 120 ?L de clorofórmio (solvente extrator) foram injetados nesta amostra aquosa e 165 ?L de fase sedimentada foram recuperados. As características de desempenho analítico para ambos os métodos foram avaliadas, sendo obtida linearidade na faixa de concentração plasmática de 1-20 ?g/mL e limite inferior de quantificação (LIQ) de 1 ?g mL-1. Os ensaios de precisão e exatidão apresentaram valores de acordo com os guias oficiais. Além disso, os métodos foram seletivos, não apresentaram efeito residual e as amostras foram estáveis. Os valores de recuperação foram de 54,3 e 23% para HF-LPME e DLLME, respectivamente. Os métodos validados foram aplicados com sucesso em amostras de plasma de pacientes epilépticos em tratamento com a LTG. Além disso, as duas técnicas foram comparadas e a HF-LPME apresentou vantagens em relação à DLLME, mostrando ser uma técnica promissora para análise de matrizes complexas, com reduzido consumo de solvente orgânico e possibilidade de automação. / Lamotrigine (LTG) is an antiepileptic drug, which belongs to the class of phenyltriazine that can be used in the treatment of new-onset and refractory epilepsy. Due to its high interindividual variability, drug interactions and the adverse effects presented during the LTG administration, therapeutic drug monitoring is very important to dose adjustment and to avoid toxicity effects. Thus, the goal of this study was to develop and validate two microextraction techniques: the hollow fiber liquid-phase microextraction (HF-LPME) and the dispersive liquid-liquid microextraction (DLLME) to analyze LTG in plasma samples of epileptic patients. First of all, the eletroforetic conditions were optimized. A fused-silica uncoated capillary with 75 ?m internal diameter, and 50 cm effective length was used. The 2-(N-morpholino)ethanesulfonic acid (MES) 130 mmol L-1 pH 5.0 was chosen as background electrolyte (BGE). The temperature and the voltage were kept constant at 20°C and 15 kV respectively. For sample injection, hydrodynamic injection mode was used, with a pressure of 0.5 psi applied for 10 s. The wavelength was set at 214 nm. Under final conditions, LTG and the internal standard (IS) lidocaine were analyzed in less than 7 minutes. HF-LPME was evaluated in the three phase mode. The analyte was extracted from 4.0 mL of a basic donor phase (composed of 500 ?L of plasma and 3.5 mL of sodium phosphate solution 50 mmol L-1 pH 9.0) into an organic phase composed of 1-octanol immobilized in the pores of the hollow fiber, and further into an acidic acceptor phase (hydrochloric acid solution pH 4.0) placed in the lumen of the fiber. To evaluate DLLME, the plasma samples were pretreated to remove the proteins, and 500 ?L of plasma sample was mixed with 1 mL of acetonitrile. After that, 1,3 mL of the upper layer was added to 4 mL of sodium phosphate solution 50 mmol L-1 pH 9.0, and 120 ?L of chloroform (extracting solvent) was rapidly injected in the aqueous sample and 165 ?L of the sedimented phase was collected. Under the optimized conditions, both methods were linear over the plasmatic concentration range of 1.0-20.0 ?g mL-1 and the lower limit of quantification (LLOQ) was 1.0 ?g mL-1. Both methods showed good precision, accuracy, selectivity to LTG, with no carryover and the samples were stable under the studied conditions. The recovery were 54,3 and 23% to HF-LPME and DLLME respectively. The validated methods were successfully applied for the quantification of LTG in plasma samples of epileptic patients. The techniques were compared and HF-LPME was more advantageous for being more suitable to analysis of complex matrices using small amount of organic solvent, and also can be automated.