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Approximately 10% of pregnant women take antidepressants. Prenatal exposure to selective serotonin reuptake inhibitors (SSRIs), a class of antidepressants, has been shown to alter serotonergic signaling in the brain. However, the effects of SSRIs on peripheral serotonin (5HT) synthesis and/or signaling have largely been ignored. Serotonin in the gut is critical for intestinal function and dysregulation of this pathway is associated with intestinal disease. Therefore, the goal of this study was to determine the effects of perinatal exposure to the SSRI fluoxetine (Prozac®) on intestinal health in the offspring. Dams were given vehicle or fluoxetine hydrochloride (FLX 10 mg/kg/d; N=15) for 2 weeks prior to mating until weaning. We assessed markers of serotonergic signaling, inflammation, and composition of the gut microbiota in the offspring. Male offspring of fluoxetine-treated dams had significantly elevated serum levels of 5-HT and decreased expression of the 5HT2A receptor and MAO. In female offspring there was no effect of SSRI exposure to alter any components of serotonergic signaling. Although we did not find any evidence of increased inflammation following fluoxetine exposure, there were significant alterations in the composition of the gut microbiota in the exposed offspring. Male offspring of SSRIs-exposed mothers had changes in key components of the gut serotonergic system in association with elevated levels of serum 5-HT and alterations in the gut microbiota in adulthood. The impact of these changes on intestinal health and the reasons for the sex specific effects remain to be determined. / Thesis / Master of Science in Medical Sciences (MSMS)

Major depressive disorder (MDD) is one of the most common psychiatric illnesses worldwide, with pharmacotherapy as a first-line option for the management of this illness. The National Center for Health Statistics found that the use of antidepressants has increased by more than 4 fold in the last 20 years. While SSRI’s act centrally to treat MDD, their peripheral effects are often overlooked. Interestingly, components of the serotonergic system including the serotonin transporter (SERT), serotonin receptors, and enzymes important for serotonin synthesis (tryptophan hydroxylase 1 and 2; Tph1 and Tph2) are affected by SSRI treatment both centrally and peripherally. This disruption of serotonin signaling in the pancreas is of particular interest as there is a considerable link between the serotonin and hedgehog signaling pathways, both of which are important for pancreatic beta cell function. I hypothesize that pancreatic beta cell exposure to the SSRI fluoxetine in vitro will lead to altered hedgehog signaling ultimately resulting in a disruption in insulin secretion. / Thesis / Master of Science in Medical Sciences (MSMS)

Master of Science / Department of Psychological Sciences / Mary Cain / Individuals suffering from depression primarily rely on pharmacological interventions to alleviate the incapacitating symptoms of the disorder. In addition to genetic differences underlying the etiology of depression, environmental factors play a key role as well. For example, environmental enrichment results in various neurotransmitter alterations, significantly affecting serotonin. To test the efficacy of novel antidepressant drugs in the preclinical laboratory setting, researchers commonly implement the forced swim test (FST) for rats or mice. However, the effect of environmental enrichment on the expression of depressive-like states in the FST is unclear, and it is unknown whether environmental enrichment or social isolation can alter the efficacy of the commonly prescribed antidepressant drug, fluoxetine. In the present study, locomotor activity and FST performance were measured after 30 days of rearing in enriched (EC), standard (SC), and isolated (IC) conditions. Results showed that regardless of the significant effect of fluoxetine on locomotor activity in EC, SC, and IC rats, fluoxetine failed to increase swimming and decrease immobility in all three environmental conditions, with enriched-fluoxetine rats displaying significantly less swimming behavior in the FST than enriched rats receiving vehicle control injections. These results suggest that differential rearing, specifically environmental enrichment, can alter the efficacy of antidepressants and may suggest that enrichment reverses the effects of fluoxetine.

Naked mole-rats are eusocial rodents that live in subterranean colonies with a strict reproductive and social hierarchy. Breeders are socially dominant and other colony members are non-reproductive subordinates. The effects of manipulating the serotonergic system on aggression are well studied in many species, but not in eusocial rodents like the naked mole-rat. For the current study, the effects of fluoxetine hydrochloride (FLX) on status-specific behaviours of subordinates (Experiment 1) and queens (Experiment 2) were evaluated both in-colony and in a social-pairing paradigm to investigate how the serotonergic system influences aggression in this species. In accordance with our main hypothesis, chronic treatment of FLX attenuated the frequency and duration of aggression in queens, but not subordinates, when paired with an unfamiliar conspecific. Further exploration of pharmacological manipulation on status-specific behaviours of this eusocial species may elucidate the neurobiological mechanisms underlying their unique and rigid social hierarchy.

Psychotropic drugs are commonly used group of pharmaceuticals, their main effect is to alter psychic condition, including mental diseases treatment. Symptoms of mental illnesses are more and more common, theref orenumber of patients diagnosed with mental illnes, and thus using psychotropics, is growing stronger. But using psychotropics during gestation is not without risks for mother and embryo itself. However, thanks to the absence of controlled human studies, the knowledge of emrbyotoxic effects of pschotropics is limited to casuistics, reported side effects and animal experimental studies. Many of those studies suggests emrbyotoxic potential of psychotropic drugs, on the other hand, others claim their safety. The goal of this thesis is to test at least some of them, using CHEST method, that allows us to observe direct effect of unmetabolized substance on chick embryo. In this thesis we tested selected psychotropics, very common antidepressant fluoxetine (prozac) and antipsychotic drug olanzapine, for embryotoxicity, using in ovo method CHEST with chick embryos as model organism. By bypassing the maternal organism and his metabolism, this method allows to observe direct effect of unmetabolized substance on chick embryo. Results revealed embryotoxic effect of fluoxetin in dosage 10-2 and 10-3 on 3rd and...

Worldwide, pharmaceutical compounds continue to increase in our aquatic environment. The predominant route into nature is through wastewater treatment plants since the elimination of residual pharmaceuticals is still not mainstream in WWTPs. Fluoxetine is an antidepressant which is commonly prescribed to treat human depression. Wastewater residual fluoxetine is typically found in waters around the world, and can thus affect exposed organisms, such as fish and invertebrates. However, how fluoxetine may affect mating behaviour in exposed organisms remains poorly understood, and particularly so in invertebrates. This is hampering our understanding of the consequences of our medicine leaking into nature because mating behaviour often affects fitness, and invertebrates are key organisms in food chains. Therefore, I here experimentally investigated long-term effects of environmental relevant concentration of fluoxetine (20 ng L-1) on mating behaviours of male and female freshwater isopod Asellus aquaticus. I demonstrate that fluoxetine reduced male mating attempts with receptive females. Further, there was a tendency for fluoxetine exposure to increase latency to form pre-copula. There was no effect of fluoxetine exposure on male latency to encounter females or female responses toward males. These results indicate that fluoxetine also can affect isopods by reducing mating behaviour. In the long-term, if reproduction is delayed or reduced, it may cause a reduction in populations and thus, alter the whole ecosystem.

Este trabalho teve por finalidade o desenvolvimento e validação de métodos para análise estereosseletiva de alguns fármacos e metabólitos, bem como a aplicação desses métodos na avaliação do potencial de fungos, principalmente endofíticos, em processos de biotransformação. Os seguintes fármacos foram selecionados para esse estudo: fluoxetina, propranolol, omeprazol, oxibutinina e ibuprofeno. Para determinação simultânea dos enantiômeros da fluoxetina (FLX) e norfluoxetina (NFLX) em meios de cultura de fungos endofíticos, empregou-se a cromatografia líquida de alta eficiência com detecção por absorção no ultravioleta, em um sistema com duas colunas em série, sendo uma de fase reversa (C18) e outra com fase estacionária quiral (Chirobiotic® V). A fase móvel foi composta por etanol: tampão acetato de amônio 15 mmol L-1, pH 5,90: acetonitrila (77,5: 17,5: 5, v/v/v) e a detecção foi realizada em 227 nm. A extração líquido-líquido foi empregada na preparação das amostras. As curvas analíticas foram lineares no intervalo de concentração de 12,5 a 3750 ng mL-1 (r 0,996) para todos os enantiômeros analisados. Os coeficientes de variação e erros relativos obtidos nos estudos de precisão e exatidão foram inferiores a 10%. Nas condições empregadas, os cinco fungos endofíticos estudados não foram capazes de promover a biotransformação da FLX (reação de demetilação). A eletroforese capilar foi empregada para análise enantiosseletiva do propranolol (PROP) e 4-hidroxipropranolol (4-OHPROP). A melhor condição de resolução dos enantiômeros foi encontrada com a aplicação de um planejamento experimental de Box-Behnken: solução de eletrólitos composta por tampão trietilamina / ácido fosfórico (TEA/H3PO4), 25 mmol L-1, pH 9,00, carboximetil--ciclodextrina 4% (m/v) como seletor quiral e análise realizada na voltagem de 17 kV. O método de extração líquido-líquido também foi empregado para preparação das amostras. As curvas analíticas foram lineares no intervalo de concentração de 0,25 a 10,0 g mL-1 para 4-OHPROP e de 0,10 a 10,0 g mL-1 para PROP, apresentando coeficientes de correlação (r) 0,995 para todos os enantiômeros analisados. Os coeficientes de variação e erros relativos obtidos nos estudos de precisão e exatidão foram inferiores a 15%. Os cinco fungos endofíticos em estudo se mostraram eficientes na biotransformação estereosseletiva do PROP, com maior formação do metabólito (-)-(S)-4-OHPROP. O fungo Glomerella cingulata (VA1), em especial, apresentou uma concentração de 1,745 g mL-1 do enantiômero (-)-(S)-4-OHPROP depois de 72 horas de incubação, ao passo que a formação do enantiômero (+)-(R)-4-OHPROP não foi observada. A utilização deste fungo em escalas ampliadas pode ser uma fonte promissora de obtenção do metabólito 4-OHPROP na forma enantiomericamente pura. A determinação simultânea de omeprazol (OMZ), 5-hidroxiomeprazol (5-HOMZ) e omeprazol sulfona (OMZ SUL) em meio de cultura Czapek Dox modificado ii tamponado foi realizada empregando um método rápido de análise por cromatografia líquida de ultra eficiência com detector por arranjo de diodos (UPLC / DAD), usando coluna monolítica de fase reversa e eluição por gradiente. OMZ, 5-HOMZ e OMZ SUL foram extraídos das amostras utilizando uma mistura de acetato de etila: t-butil metil éter (9: 1, v/v). A separação foi obtida empregando uma coluna RP 18 Chromolith Fast Gradient endcapped e fase móvel constituída por 0,15% (v/v) de ácido trifluoroacético (TFA) em água (solvente A) e 0,15% (v/v) de TFA em acetonitrila (solvente B). Os tempos de retenção foram de 0,70 min para 5-HOMZ, 0,74 min para OMZ, 0,77 min para OMZ SUL e 0,91 min para o padrão interno (bupropiona, BUP). O método foi linear no intervalo de 0,2 a 10,0 g mL-1 (r 0,995) para todos os analitos. O processo de biotransformação foi realizado durante apenas 24 horas de incubação, por causa de problemas de estabilidade do OMZ. Por esse mesmo motivo, a biotransformação estereosseletiva não foi avaliada. Apenas três fungos apresentaram formação do metabólito 5-HOMZ, e dentre estes, apenas o fungo Botritis cinerea (BC) produziu esse metabólito em concentração superior ao limite de quantificação do método. A formação do metabólito OMZ SUL foi observada para todos os fungos, exceto para Glomerella cingulata (VA1) e Guignardia mangiferae (VA15). Esses fungos podem ser úteis para a obtenção dos metabólitos do OMZ, mas estudos detalhados do comportamento do fármaco nas condições de cultivo são necessários, uma vez que este substrato pode sofrer degradação em meio ácido e na presença de luz. A análise simultânea dos enantiômeros da oxibutinina (OXY) e da N-desetiloxibutinina (DEOB) em meio de cultura Czapek foi obtida empregando a cromatografia líquida de alta eficiência com detector UV (HPLC/UV). Os analitos foram separados usando coluna quiral Chiralpak AD e fase móvel constituída por hexano: isopropanol: etanol: dietilamina (94: 4: 2: 0,05, v/v/v/v) e detectados em 210 nm. Um estudo piloto de biotransformação empregando os mesmos fungos e as condições de biotransformação utilizadas para os demais fármacos mostrou que não houve a formação do metabólito de interesse. Além disso, não houve uma diminuição significativa da concentração de OXY durante o período de incubação, o que poderia ser um indicativo da formação de outros metabólitos não monitorados nas condições de análise. Como a reação de desetilação da OXY para formar a DEOB não foi observada nos experimentos, não foi necessário realizar a validação do método analítico. A separação simultânea do ibuprofeno (IBP), dos enantiômeros do 2-hidroxi-ibuprofeno (2-OH-IBP) e dos estereoisômeros do carboxi-ibuprofeno (COOH-IBP) foi realizada empregando-se uma coluna Chiralpak AS-H e fase móvel constituída por hexano: isopropanol: TFA (95: 5: 0,1, v/v/v). O solvente extrator usado na extração líquido-líquido foi uma mistura de hexano: acetato de etila (1: 1, v/v). A detecção foi feita por espectrometria de massas (MS/MS), com a fonte de ionização por eletronebulização operada no modo positivo (ESI+). O método foi linear nos intervalos de 0,1 a 20,0 g mL-1 para IBP, de 0,05 a 7,5 g mL-1 para o cada enantiômero do 2-OH-IBP e de 0,025 a 5,0 g mL-1 para cada estereoisômero do COOH-IBP. Os demais parâmetros de validação obtidos para o método apresentaram-se dentro dos limites recomendados pela literatura. Os sete fungos endofíticos estudados se mostraram eficientes na biotransformação do IBP em seu principal metabólito 2-OH-IBP, mas apenas os fungos Nigrospora sphaerica (SS67) e Chaetomium globosum (VR10) iii biotransformaram o IBP de forma enantiosseletiva mais acentuada, observando-se maior formação do metabólito ativo (+)-(S)-2-OH-IBP. A não estereosseletividade observada para os demais fungos pode ser indício de uma possível conversão quiral do fármaco, similar a que ocorre em humanos. A formação dos estereoisômeros do COOH-IBP não foi observada, provavelmente, porque sua rota de formação envolve uma seqüência de reações. Os resultados apresentados nesse trabalho mostram que fungos, particularmente os endofíticos, podem ser uma fonte promissora para obtenção de metabólitos de fármacos, inclusive de forma enantiomericamente pura. / This work aimed the development and validation of suitable methods for the stereoselective analysis of some drugs and metabolites, as well as, the application of these methods to assess the potential of fungi, mainly the endophytic ones, in biotransformation processes. The following drugs were selected for this study: fluoxetine, propranolol, omeprazole, oxybutynin and ibuprofen. The simultaneous determination of fluoxetine (FLX) and norfluoxetine (NFLX) enantiomers in culture media of endophytic fungi was carried out by high-performance liquid chromatography with UV-detection, in a system of two columns coupled in series, in which one of them was a reversed phase (C18) column and the another one was a chiral stationary phase column (Chirobiotic ® V). The mobile phase consisted of ethanol: ammonium acetate buffer, 15 mol L-1, pH 5.90: acetonitrile (77.5: 17.5: 5, v/v/v) and the detection was performed at 227 nm. Liquid-liquid extraction was employed for sample preparation. The analytical curves were linear over the concentration range of 12.5 to 3750 ng mL-1 (r 0.996) for all enantiomers evaluated. The coefficients of variation and relative errors obtained in the evaluation of method precision and accuracy were lower than 10%. In the studied conditions, the five endophytic fungi used were not able to perform the biotransformation of FLX (demethylation reaction). Capillary electrophoresis was employed for the enantioselective analysis of propranolol (PROP) and 4-hydroxypropranolol (4-OHPROP). The best condition for enantiomer resolution was obtained by applying an experimental design of Box-Behnken: electrolyte solution composed of triethylamine / phosphoric acid (TEA/H3PO4) buffer, 25 mmol L-1, pH 9.00, with 4% (w/v) carboxymethyl--cyclodextrin as the chiral selector and analysis performed at 17 kV. Liquid-liquid extraction was also used for sample preparation. The analytical curves were linear over the concentration range of 0.25 to 10.0 g mL-1 for 4-OHPROP and 0.10 to 10.0 g mL-1 for PROP, presenting correlation coefficients (r) 0.995 for all enantiomers evaluated. The coefficients of variation and relative errors obtained in the evaluation of precision and accuracy were lower than 15%. All the five endophytic fungi (Phomopsis sp. (TD2), Glomerella cingulata (VA1), Penicillium crustosum (VR4), Chaetomium globosum (VR10) and Aspergillus fumigatus (VR12)) showed effectiveness in the stereoselective biotransformation of PROP, with higher formation of (-)-(S)-4-OH-PROP. The fungus Glomerella cingulata (VA1), in particular, showed a concentration of 1.745 g mL-1 for the enantiomer (-)-(S)-4-OHPROP after 72 hours of incubation, whereas there was no formation of the enantiomer (+)-(R)-4-OHPROP. Therefore, the use of this fungus in large scale may be a promising source to obtain 4-OHPROP in the enantiomerically pure form. A fast analytical method based on ultra-performance liquid chromatography / diode array detector (UPLC/DAD) using a monolithic reversed phase column and gradient elution was developed for the simultaneous determination of omeprazole (OMZ), 5-hydroxyomeprazole (5-HOMZ) and omeprazole sulfone (OMZ SUL) in modified and buffered Czapek-Dox culture medium. OMZ, 5-HOMZ and OMZ SUL were extracted using a mixture of ethyl acetate: methyl t-butyl ether (9: 1, v/v). The separation was achieved using a Chromolith Fast Gradient RP 18 endcapped column with the mobile phase consisting of 0.15% (v/v) trifluoroacetic acid (TFA) in water (solvent A) and 0.15% (v/v) TFA in acetonitrile (solvent B). Retention times were 0.70 min for 5-HOMZ, 0.74 min for OMZ, 0.77 min for OMZ SUL and 0.91 min for internal standard (bupropion, BUP). The method was linear over the concentration range of 0.2 to 10.0 g mL-1 (r 0.995) for all analytes. The biotransformation process was carried out only within 24 hours of incubation, due to OMZ instability. For the same reason, the stereoselectivity in this process was not evaluated. The formation of the metabolite 5-HOMZ was observed only for three fungi, and among them, only the fungus Botrytis cinerea (BC) produced this metabolite in concentrations higher than the limit of quantification. The formation of OMZ SUL was observed for all fungi, except for Guignardia mangiferae (VA1) and Glomerella cingulata (VA15). The fungi evaluated in this study can be useful to obtain the metabolites of OMZ, but detailed study of the drug stability in culture conditions is required, since this substrate can undergo degradation in acidic conditions and in the presence of light. The simultaneous analysis of oxybutinin (OXY) and N-desethyloxybutinin (DEOB) enantiomers in Czapek culture medium was carried out by liquid chromatography with UV detection (HPLC/UV). The analytes were separated using a Chiralpak AD column employing as mobile phase hexane: isopropanol: ethanol: diethylamine (94: 4: 2: 0.05, v/v/v/v) and detection at 210 nm. A pilot study of biotransformation using the same fungi and conditions employed for the biotransformation of the other drugs showed that the metabolite of interest was not formed. Moreover, the decrease in the concentration of OXY, which could be indicative of the formation of other metabolites not monitored under the conditions of analysis, was not observed. Since the reaction of OXY desethylation to form DEOB was not observed in the experiments, the validation of the analytical method was not required. The method for the simultaneous analysis of ibuprofen (IBP), 2-hydroxyibuprofen (2-OH-IBP) enantiomers and carboxyibuprofen (IBP-COOH) stereoisomers was developed using a Chiralpak AS-H column and a mobile phase consisting of hexane: isopropanol: TFA (95: 5: 0.1, v/v/v). A mixture of hexane: ethyl acetate (1: 1, v/v) was used as solvent extractor for sample preparation. The detection was performed by tanden mass spectrometry (MS/MS) with the electrospray interface operated in the positive mode (ESI+). The method was linear over the concentration range of 0.1 to 20.0 g mL-1 for IBP, 0.05 to 7.5 g mL-1 for each 2-OH-IBP enantiomer and 0.025 to 5.0 g mL-1 for each COOH-IBP stereoisomer. The other validation parameters studied were within the limits established in the literature. The seven studied endophytic fungi showed to be efficient in the biotransformation of IBP to its main metabolite 2-OH-IBP, however, only the fungi Nigrospora sphaerica (SS67) and Chaetomium globosum (VR10) biotransformed IBP enantioselectively, with greater formation of the active metabolite (+)-(S)-2-OH-IBP. The lack of stereoselectivity observed for the other fungi could be caused by a possible chiral inversion process occurring for IBP, in a similar way that happens in humans. The formation of COOH-IBP stereoisomers was not observed probably because the route of formation of this metabolite requires a sequence of reactions. The results presented here show that fungi, particularly the endophytic ones, may be a promising source to obtain the metabolites of drugs, including in their enantiomerically pure form.

O estudo teve como objetivos avaliar a melhora precoce em uma e duas semanas no tratamento com quatro diferentes antidepressivos e placebo, assim como avaliar as medidas de acurácia da melhora precoce como preditor de resposta e remissão em oito semanas de tratamento em pacientes com TDM. Poucos estudos fizeram essa comparação. Para a análise foram utilizadas amostras de bancos de dados de quatro ensaios clínicos com dados de resposta ao tratamento com sertralina (n=50), venlafaxina (n=67), mirtazapina (n=28), fluoxetina (n=17), placebo (n=42). Todos pacientes foram avaliados pela escala de avaliação de Hamilton de 17 itens ao início do tratamento e após uma, duas e oito semanas. A ocorrência da melhora precoce foi avaliada de seis formas, utilizando-se os pontos de corte sugeridos pelo relatório da força tarefa da ISBD para avaliação de curso e desfecho. As variáveis relativas à melhora precoce estão relacionadas a seguir: (a) melhora precoce em uma semana >= 25%; (b) melhora precoce em uma semana >= 25% e < 50%; (c) melhora precoce em uma semana >= 50%; (d) melhora precoce em duas semanas >= 25%; (d) melhora precoce em duas semanas >= 25% e < 50%; (f) melhora precoce em duas semanas >= 50%. As variáveis de desfecho testadas quanto a associação com melhora precoce foram duas: (a) resposta em oito semanas (melhora >= 50%); (b) remissão em oito semanas (HAM-D-17 <= 7). Para cada par de variáveis foram calculados o valor preditivo positivo, valor preditivo negativo, sensibilidade, especificidade e acurácia. A associação foi testada pelo teste qui-quadrado de Pearson ou pelo teste exato de Fisher. Em todos os grupos houve porcentagem considerável de pacientes que apresentaram melhora precoce em uma ou duas semanas, com destaque para mirtazapina, em que 53,57% dos pacientes apresentaram algum tipo de melhora precoce em uma semana e 71,43% dos pacientes apresentaram melhora precoce em duas semanas. Ao final de duas semanas o grupo que apresentou maior taxa de melhora precoce foi o grupo tratado com venlafaxina (73,13%). Foi encontrada associação da melhora precoce em uma semana com resposta em oito semanas ao nível de significância de 5% no grupo tratado com mirtazapina e no grupo que reúne todos antidepressivos. No grupo tratado com mirtazapina a melhora precoce maior ou igual a 25% tem alto valor preditivo positivo (0,94), porém baixo valor preditivo negativo (0,58). A melhora precoce em uma semana está associada à remissão em oito semanas nos tratamentos com venlafaxina e mirtazapina. Os resultados mais consistentes ocorreram no teste da associação entre melhora precoce em duas semanas e resposta em oito semanas, na qual foi encontrada associação entre as variáveis em todos os antidepressivos (exceção à fluoxetina). A melhora precoce com Mirtazapina foi a que apresentou o maior valor preditivo positivo e a melhor medida de acurácia, de 0,86, resultado mais consistente em toda a amostra analisada. Com placebo foi encontrada associação entre melhora precoce maior que 50% e resposta em oito semanas. O baixo valor preditivo positivo indica que essa melhora sustenta-se em oito semanas menos do que nos grupos tratados com antidepressivo. O valor preditivo negativo foi de 0,81, o maior entre todos os grupos, significando que quando há melhora com placebo, em geral ela ocorre em até duas semanas. Nos testes da melhora precoce em duas semanas como preditor de remissão foram encontrados resultados mais significativos na melhora precoce maior que 50% com diferentes acurácias em cada grupo. O antidepressivo com resultados mais robustos foi a mirtazapina, com uma acurácia de 0,86. Tanto no grupo tratado com mirtazapina quanto no grupo tratado sertralina tivemos altos valores preditivos negativos, respectivamente 0,89 e 0,83, indicando que ausência de melhora rápida maior que 50% diminui muito as chances de remissão / This study aimed to evaluate the early improvement in one and two weeks\' treatment with four different antidepressants and placebo, as well as evaluate the measures of accuracy of early improvement as a predictor response and remission in eight weeks of treatment with TDM patients. Few studies have done this comparison. For this analysis, data samples from four clinical trials with treatment response with sertraline (n = 50), venlafaxine (n = 67), mirtazapine (n = 28), fluoxetine (n = 17), placebo (n = 42). All patients were evaluated at baseline on the 17 item Hamilton Rating Scale of Depression (HAM-D 17) in the begging of the treatment and after one, two and eight weeks. The occurrence of early improvement was evaluated in six ways, using the cut-off points suggested by the ISBD task force report for course and outcome evaluation. The variables related to early improvement are listed below: (a) early improvement in one week >= 25%; (b) early improvement in one week >= 25% and < 50%; (c) early improvement in one week >= 50%; (d) early improvement in two weeks >= 25%; (d) early improvement in two weeks >= 25% and < 50%; (f) early improvement in two weeks >= 50%. The outcome variables tested in association with early improvement were two: (a) response at eight weeks (improvement >= 50%); (B) remission in eight weeks (HAM-D-17 <= 7). For each pair of variables were calculated the positive predictive value, negative predictive value, sensitivity, specificity and accuracy. The association was tested by Pearson\'s chi-square test or by Fisher\'s exact test. In all groups, there was considerable percentage of patients that achieved early improvement in one or two weeks, especially mirtazapine, in which 53.57% of the patients achieved early improvement in one week and 71.43% of the patients achieved early improvement in two weeks. At the end of two weeks the group that presented the highest rate of early improvement was the group treated with venlafaxine (73.13%). We found an association of early improvement in one week with an 8-week response at a significance level of 5% in the mirtazapine group. In the group treated with mirtazapine, early improvement greater than or equal 25% had high PPV (0.94), but low NPV (0.58). The early improvement in 1 week was associated to the 8 weeks remission on treatments with venlafaxine and mirtazapine. The most consistent results occurred on the association test between early improvement in two weeks and response in eight weeks, where an association between variables in all antidepressants (except fluoxetine) was found. Mirtazapine was the antidepressant that presented the highest VPP and the best measures of accuracy, of 0,86, the most consistent of all sample analyzed. With placebo, an association was found between early improvement higher than 50% and response in eight weeks. The low VPP indicates that this improvement sustains itself in eight weeks less than groups treated with antidepressant. VPP was 0,81, the highest among all groups, meaning that when there is improvement with placebo, in general it occurs in up to two weeks. Less robust results were found for the early improvement in two weeks as a remission predictor. In the tests of early improvement in two weeks as a predictor of remission, more significant results were found in early improvement higher than 50% with different accuracies in each group. The antidepressant with the most robust results was mirtazapine, with an accuracy of 0,86. Both in the group treated with mirtazapine and the one treated with sertraline, we had high VPN, 0,89 and 0,83 respectively, indicating that the lack of quick improvement higher than 50% diminishes the chances of remission significantly