Anlodipina e diclofenaco podem ser combinados de forma que o potencial de interação é alto. Investigamos se anlodipina interfere com o efeito antimigratório do diclofenaco em ratos espontaneamente hipertensos (SHR) e ratos wistar. Os ratos foram tratados (15 dias) com diclofenaco e anlodipina, juntos ou separadamente. A migração leucocitária foi estudada por microscopia intravital e a expressão de moléculas de aderência por imunohistoquímica. A anlodipina reduziu migração leucocitária em SHR e ratos wistar por reduzir a expressão de ICAM-1 em células endoteliais venulares. A redução da migração leucocitária em ratos wistar pode decorrer também da redução da expressão de PECAM-1 em células endoteliais. A combinação reduziu o efeito do diclofenaco sobre a migração em SHR e wistar. Em SHR esse efeito envolveu a redução de ICAM-1. A redução da PA causada pela anlodipina em SHR parece contribuir para a redução da migração leucocitária. Interação farmacocinética foi excluída. / Amlodipine and diclofenac may be combined so the potential for interaction of both is high. We determined if amlodipine interferes with the antimigratory effect of diclofenac in spontaneously hypertensive rats (SHR) and wistar rats. Rats were treated with either diclofenac or amlodipine alone or combined (for 15 days). Leukocyte migration was evaluated by intravital microscopy and cell adherence molecules expression by immunohistochemistry. Amlodipine reduces migration in both SHR and wistar rats by reducing venular endothelial cell ICAM-1 expression. In wistar the antimigratory effect of amlodipine may also be due to reduction in PECAM-1 expression. Diclofenac effect was reduced by amlodipine in both SHR and wistar. In SHR amlodipine reduces the effect of diclofenac by impairing its reducing effect on ICAM-1. Reduction of the BP levels seems to contribute to reduction of the leukocyte migration caused by amlodipine in SHR. Pharmacokinetic interaction was excluded.

A biodisponibilidade é definida pelos parâmetros de velocidade e extensão com que o fármaco atinge a circulação sistêmica a partir da forma farmacêutica, sendo uma propriedade não somente do fármaco, mas também da formulação, representando o desempenho in vivo da qualidade do medicamento. O medicamento genérico, para ser intercambiável com sua referência (geralmente o inovador registrado após comprovação de eficácia e segurança), deve ser considerado pelas autoridades regulatórias como seu equivalente terapêutico. A bioequivalência é o estudo comparativo das biodisponibilidades entre medicamentos, empregado para comprovação de equivalência terapêutica, baseada no princípio de que a similaridade dos perfis sanguíneos de concentração-tempo proporciona similares resultados quanto à eficácia e segurança. O presente trabalho compreendeu uma abordagem sobre os estudos de biodisponibilidade e bioequivalência com alimentação, com objetivo de sistematização dos fundamentos científicos e critérios normativos nacionais e internacionais, avaliação da necessidade e elaboração de diretrizes para condução destes estudos. Foi pesquisada a literatura científica sobre o tema, com ênfase nas publicações dos últimos dez anos, e também as diretrizes regulatórias nacionais e internacionais vigentes. Foram avaliados os efeitos do alimento na absorção gastrintestinal de fármacos, os fatores envolvidos na interação fármaco-alimento e os mecanismos físico-químicos e fisiológicos envolvidos. O alimento pode influenciar a absorção dos fármacos e promover aumento, retardo ou redução de absorção, devido a diferentes efeitos, por exemplo: prolongamento do tempo de esvaziamento gástrico, interação direta do fármaco com constituintes do alimento, aumento da viscosidade do conteúdo intestinal, alteração do pH, aumento do fluxo sanguíneo esplâncnico e interação com transportadores. A interação fármaco-alimento pode resultar em alterações farmacocinéticas e farmacodinâmicas. O efeito do alimento é mais significativo nas fases de absorção e metabolismo do fármaco, podendo resultar em perda de eficácia ou toxicidade. As interações fármaco-alimento são influenciadas pela natureza do alimento, constituição e quantidade da refeição, tempo entre alimentação e medicação e pela formulação. A refeição altamente gordurosa tem maior potencial de alteração da fisiologia gastrintestinal, principalmente aumentando o tempo de esvaziamento gástrico, o fluxo sanguíneo e a secreção biliar. Esses efeitos podem afetar significativamente a absorção de fármacos, sendo especialmente críticos para as formulações de liberação modificada. O efeito total do alimento na farmacocinética é resultante da interação de múltiplos efeitos relacionados ao fármaco, à formulação, à fisiologia gastrintestinal e à refeição. Devido à variabilidade e difícil previsibilidade dos efeitos do alimento sobre a velocidade e extensão de absorção dos fármacos, devem ser conduzidos estudos de efeito do alimento para novos fármacos e novas formulações. A pesquisa resultou na compilação das diretrizes para avaliação do efeito do alimento na biodisponibilidade, incluindo-se os desenhos dos estudos. É apresentado um esquema para avaliação da necessidade dos estudos de biodisponibilidade e bioequivalência, com base nas características do fármaco e nos tipos de formulações. As diretrizes para requerimento e condução dos estudos foram sistematizadas em uma proposta de guia para estudos de biodisponibilidade e bioequivalência com alimentação a ser empregado no caso de registro e alterações pós-registro para medicamentos novos, genéricos e similares no Brasil. / Bioavailability is defined by rate and extension parameters with which the drug reaches the systemic circulation from its dosage form, being not only a property of such drug, but also of the formulation, representing the in vivo quality of the medicine. In order to be interchangeable with its reference drug (usually the innovative drug registered after efficacy and safety proof), the generic drug must be considered as its therapeutic equivalent. Bioequivalence is the comparative study between drugs\' bioavailabilities, used for the proving of therapeutic equivalence, based on the principle that the similarity between blood concentration-time profiles generates similar efficacy and safety results. This work is a discussion about the food-effect bioavailability and fed bioequivalence studies, aiming at systematizing the scientific fundaments and national and international regulatory criteria, necessity evaluation and elaboration of de guidelines for studies execution. Research was done on scientific literature on the subject, with emphasis on publications over the last ten years, and also on current regulatory guidelines. The effects of food on the gastrointestinal absorption of the drugs, the factors related to the food-drug interaction and the physical-chemical and physiological mechanisms involved were evaluated. Food may influence the drug absorption and cause drug absorption increase, delay or reduction due to different factors, for example: gastric emptying time increase, direct drug interaction with food constituents, intestinal content viscosity increase, pH alterations, spleen blood flow increase and transporter interaction. The food-drug interaction may cause pharmacokinectic and pharmacodynamics alterations. Food\'s effect is most significant during the absorption and metabolic phases of the drug and may result in efficacy loss or toxicity. The food-drug interaction is influenced by the nature of the food, meal constitution and quantity, feeding and medication interval time and formulation. A high-fat meal has greater gastrointestinal physiology alteration potential, especially increasing the gastric emptying time, the blood flow and bile secretion. These effects may significantly impact the drugs\' absorption being especially critical for the modified-release formulations. Toe total food effect on pharmacokinectic is the result of the interaction of multiple effects related to the drug, the formulation, the gastrointestinal physiology and the meal. Due to its variability and the difficulty to predict the effects of food on the rate and extension of drugs\' absorption effect studies must be carried out for new drugs and new formulations. The research resulted in the compilation of the guidelines for the evaluation of food effects on bioavailability, including the studies\' designs. A scheme is presented for the evaluation of the necessity of bioavailability and bioequivalence studies based on the drug\'s characteristics and the types of formulations. The guidelines for the requirement and conduction of the studies were systematized in a guide proposal for bioavailability and bioequivalence studies of medicines with feeding to be used in the case of registration, and post-registration changes for new, generic and similar drugs in Brazil.

A biodisponibilidade é definida pelos parâmetros de velocidade e extensão com que o fármaco atinge a circulação sistêmica a partir da forma farmacêutica, sendo uma propriedade não somente do fármaco, mas também da formulação, representando o desempenho in vivo da qualidade do medicamento. O medicamento genérico, para ser intercambiável com sua referência (geralmente o inovador registrado após comprovação de eficácia e segurança), deve ser considerado pelas autoridades regulatórias como seu equivalente terapêutico. A bioequivalência é o estudo comparativo das biodisponibilidades entre medicamentos, empregado para comprovação de equivalência terapêutica, baseada no princípio de que a similaridade dos perfis sanguíneos de concentração-tempo proporciona similares resultados quanto à eficácia e segurança. O presente trabalho compreendeu uma abordagem sobre os estudos de biodisponibilidade e bioequivalência com alimentação, com objetivo de sistematização dos fundamentos científicos e critérios normativos nacionais e internacionais, avaliação da necessidade e elaboração de diretrizes para condução destes estudos. Foi pesquisada a literatura científica sobre o tema, com ênfase nas publicações dos últimos dez anos, e também as diretrizes regulatórias nacionais e internacionais vigentes. Foram avaliados os efeitos do alimento na absorção gastrintestinal de fármacos, os fatores envolvidos na interação fármaco-alimento e os mecanismos físico-químicos e fisiológicos envolvidos. O alimento pode influenciar a absorção dos fármacos e promover aumento, retardo ou redução de absorção, devido a diferentes efeitos, por exemplo: prolongamento do tempo de esvaziamento gástrico, interação direta do fármaco com constituintes do alimento, aumento da viscosidade do conteúdo intestinal, alteração do pH, aumento do fluxo sanguíneo esplâncnico e interação com transportadores. A interação fármaco-alimento pode resultar em alterações farmacocinéticas e farmacodinâmicas. O efeito do alimento é mais significativo nas fases de absorção e metabolismo do fármaco, podendo resultar em perda de eficácia ou toxicidade. As interações fármaco-alimento são influenciadas pela natureza do alimento, constituição e quantidade da refeição, tempo entre alimentação e medicação e pela formulação. A refeição altamente gordurosa tem maior potencial de alteração da fisiologia gastrintestinal, principalmente aumentando o tempo de esvaziamento gástrico, o fluxo sanguíneo e a secreção biliar. Esses efeitos podem afetar significativamente a absorção de fármacos, sendo especialmente críticos para as formulações de liberação modificada. O efeito total do alimento na farmacocinética é resultante da interação de múltiplos efeitos relacionados ao fármaco, à formulação, à fisiologia gastrintestinal e à refeição. Devido à variabilidade e difícil previsibilidade dos efeitos do alimento sobre a velocidade e extensão de absorção dos fármacos, devem ser conduzidos estudos de efeito do alimento para novos fármacos e novas formulações. A pesquisa resultou na compilação das diretrizes para avaliação do efeito do alimento na biodisponibilidade, incluindo-se os desenhos dos estudos. É apresentado um esquema para avaliação da necessidade dos estudos de biodisponibilidade e bioequivalência, com base nas características do fármaco e nos tipos de formulações. As diretrizes para requerimento e condução dos estudos foram sistematizadas em uma proposta de guia para estudos de biodisponibilidade e bioequivalência com alimentação a ser empregado no caso de registro e alterações pós-registro para medicamentos novos, genéricos e similares no Brasil. / Bioavailability is defined by rate and extension parameters with which the drug reaches the systemic circulation from its dosage form, being not only a property of such drug, but also of the formulation, representing the in vivo quality of the medicine. In order to be interchangeable with its reference drug (usually the innovative drug registered after efficacy and safety proof), the generic drug must be considered as its therapeutic equivalent. Bioequivalence is the comparative study between drugs\' bioavailabilities, used for the proving of therapeutic equivalence, based on the principle that the similarity between blood concentration-time profiles generates similar efficacy and safety results. This work is a discussion about the food-effect bioavailability and fed bioequivalence studies, aiming at systematizing the scientific fundaments and national and international regulatory criteria, necessity evaluation and elaboration of de guidelines for studies execution. Research was done on scientific literature on the subject, with emphasis on publications over the last ten years, and also on current regulatory guidelines. The effects of food on the gastrointestinal absorption of the drugs, the factors related to the food-drug interaction and the physical-chemical and physiological mechanisms involved were evaluated. Food may influence the drug absorption and cause drug absorption increase, delay or reduction due to different factors, for example: gastric emptying time increase, direct drug interaction with food constituents, intestinal content viscosity increase, pH alterations, spleen blood flow increase and transporter interaction. The food-drug interaction may cause pharmacokinectic and pharmacodynamics alterations. Food\'s effect is most significant during the absorption and metabolic phases of the drug and may result in efficacy loss or toxicity. The food-drug interaction is influenced by the nature of the food, meal constitution and quantity, feeding and medication interval time and formulation. A high-fat meal has greater gastrointestinal physiology alteration potential, especially increasing the gastric emptying time, the blood flow and bile secretion. These effects may significantly impact the drugs\' absorption being especially critical for the modified-release formulations. Toe total food effect on pharmacokinectic is the result of the interaction of multiple effects related to the drug, the formulation, the gastrointestinal physiology and the meal. Due to its variability and the difficulty to predict the effects of food on the rate and extension of drugs\' absorption effect studies must be carried out for new drugs and new formulations. The research resulted in the compilation of the guidelines for the evaluation of food effects on bioavailability, including the studies\' designs. A scheme is presented for the evaluation of the necessity of bioavailability and bioequivalence studies based on the drug\'s characteristics and the types of formulations. The guidelines for the requirement and conduction of the studies were systematized in a guide proposal for bioavailability and bioequivalence studies of medicines with feeding to be used in the case of registration, and post-registration changes for new, generic and similar drugs in Brazil.

Background: Drug interactions resulting in adverse drug reactions (ADRs) represent a major health problem both for individuals and society in general. Post-marketing pharmacovigilance reporting databases with compiled individual case safety reports (ICSRs) have been shown to be particularly useful in the detection of novel drug - ADR combinations, though these reports have not been fully used to detect adverse drug interactions. Aim: To explore the potential to identify drug interactions using ICSRs and to develop a method to facilitate the detection of adverse drug interaction signals in the WHO Global ICSR Database, VigiBase. Methods: All six studies included in this thesis are based on ICSRs available in VigiBase. Two studies aimed to characterise drug interactions reported in VigiBase. In the first study we examined if contraindicated drug combinations (given in a reference source of drug interactions) were reported on the individual reports in the database, and in the second study we examined the scientific literature for interaction mechanisms for drug combinations most frequently co-reported as interacting in VigiBase. Two studies were case series analyses where the individual reports were manually reviewed. The two remaining studies aimed to develop a method to facilitate detection of novel adverse drug interactions in VigiBase. One examined what information (referred to as indicators) was reported on ICSRs in VigiBase before the interactions became listed in the literature. In the second methodological study, logistic regression was used to set the relative weights of the indicators to form triage algorithms. Three algorithms (one completely data driven, one semi-automated and one based on clinical knowledge) based on pharmacological and reported clinical information and the relative reporting rate of an ADR with a drug combination were developed. The algorithms were then evaluated against a set of 100 randomly selected case series with potential adverse drug interactions. The algorithm’s performances were then evaluated among DDAs with high coefficients. Results: Drug interactions classified as contraindicated are reported on the individual reports in VigiBase, although they are not necessarily recognised as interactions when reported. The majority (113/123) of drug combinations suspected for being responsible for an ADR were established drug interactions in the literature. Of the 113 drug interactions 46 (41%) were identified as purely pharmacodynamic; 28 (25%) as pharmacokinetic; 18 (16%) were a mix of both types and for 21 (19%) the mechanism have not yet been identified. Suspicions of a drug interaction explicitly noted by the reporter are much more common for known adverse drug interactions than for drugs not known to interact. The clinical evaluation of the triage algorithms showed that 20 were already known in the literature, 30 were classified as signals and 50 as not signals. The performance of the semi-automated and the clinical algorithm were comparable. In the end the clinical algorithm was chosen. At a relevant level, 38% were of the adverse drug interactions were already known in the literature and of the remaining 80% were classified as signals for this algorithm. Conclusions: This thesis demonstrated that drug interactions can be identified in large post-marketing pharmacovigilance reporting databases. As both pharmacokinetic and pharmacodynamic interactions were reported on ICSRs the surveillance system should aim to detect both. The proposed triage algorithm had a high performance in comparison to the disproportionality measure alone.

Anlodipina e diclofenaco podem ser combinados de forma que o potencial de interação é alto. Investigamos se anlodipina interfere com o efeito antimigratório do diclofenaco em ratos espontaneamente hipertensos (SHR) e ratos wistar. Os ratos foram tratados (15 dias) com diclofenaco e anlodipina, juntos ou separadamente. A migração leucocitária foi estudada por microscopia intravital e a expressão de moléculas de aderência por imunohistoquímica. A anlodipina reduziu migração leucocitária em SHR e ratos wistar por reduzir a expressão de ICAM-1 em células endoteliais venulares. A redução da migração leucocitária em ratos wistar pode decorrer também da redução da expressão de PECAM-1 em células endoteliais. A combinação reduziu o efeito do diclofenaco sobre a migração em SHR e wistar. Em SHR esse efeito envolveu a redução de ICAM-1. A redução da PA causada pela anlodipina em SHR parece contribuir para a redução da migração leucocitária. Interação farmacocinética foi excluída. / Amlodipine and diclofenac may be combined so the potential for interaction of both is high. We determined if amlodipine interferes with the antimigratory effect of diclofenac in spontaneously hypertensive rats (SHR) and wistar rats. Rats were treated with either diclofenac or amlodipine alone or combined (for 15 days). Leukocyte migration was evaluated by intravital microscopy and cell adherence molecules expression by immunohistochemistry. Amlodipine reduces migration in both SHR and wistar rats by reducing venular endothelial cell ICAM-1 expression. In wistar the antimigratory effect of amlodipine may also be due to reduction in PECAM-1 expression. Diclofenac effect was reduced by amlodipine in both SHR and wistar. In SHR amlodipine reduces the effect of diclofenac by impairing its reducing effect on ICAM-1. Reduction of the BP levels seems to contribute to reduction of the leukocyte migration caused by amlodipine in SHR. Pharmacokinetic interaction was excluded.

Soluble guanylyl cyclase (sGC) is the receptor for nitric oxide and a highly sought-after therapeutic target for the management of cardiovascular diseases. New compounds that stimulate sGC show clinical promise, but where these stimulator compounds bind and how they function remains unknown. Here, using a photolyzable diazirine derivative of a novel stimulator compound, IWP-051, and MS analysis, we localized drug binding to the 1 heme domain of sGC proteins from the hawkmoth Manduca sexta and from human. Covalent attachments to the stimulator were also identified in bacterial homologs of the sGC heme domain, referred to as H-NOX domains, including those from Nostoc sp. PCC 7120, Shewanella oneidensis, Shewanella woodyi, and Clostridium botulinum, indicating that the binding site is highly conserved. The identification of photoaffinity-labeled peptides was aided by a signature MS fragmentation pattern of general applicability for unequivocal identification of covalently attached compounds. Using NMR, we also examined stimulator binding to sGC from M. sexta and bacterial H-NOX homologs. These data indicated that stimulators bind to a conserved cleft between two subdomains in the sGC heme domain. L12W/T48W substitutions within the binding pocket resulted in a 9-fold decrease in drug response, suggesting that the bulkier tryptophan residues directly block stimulator binding. The localization of stimulator binding to the sGC heme domain reported here resolves the longstanding question of where stimulators bind and provides a path forward for drug discovery.

Drug-drug interactions (DDI) represent a growing concern for the health units. Therefore, monitoring of pharmaceutical prescriptions in hospitals can rationalize pharmacotherapy. To evaluate the effect of pharmaceutical intervention in identifying and managing drug interactions in an intensive care unit (ICU), in Northeastern of Brazil. Methods: Initially, we performed a systematic review from the search of electronic databases, Jan. 1960 to Aug 2010. After that, we realized a longitudinal study in the ICU, in a private hospital in the city of Aracaju-SE, between 2008 and 2009, which was identified in the prevalence and clinical relevance of the DDI. During the study pharmaceutical interventions were aimed at the management of DDI. The systematic review, only seven articles met all inclusion criteria and the specific sample sizes ranged from 200 to 1785 patients. As for the longitudinal study, 6085 prescriptions were collected, of which 213 contained DDI clinically relevant. Of these 178 were moderate and 35 major severity. The clinical pharmacy interventions consisted in the preparation of reports for physicians, allowing the reduction of 40% of all DDI. The data obtained allow inferring that the participation of clinical pharmacists in the DDIs identification and management may have been essential to promote the safety of ICU patients. / As interações medicamentosas (IM) representam uma crescente preocupação para as unidades de saúde. Por isso, o acompanhamento farmacêutico das prescrições nos hospitais pode racionalizar a farmacoterapia. Avaliar o efeito da intervenção farmacêutica na identificação e manejo de interações medicamentosas em uma unidade de terapia intensiva (UTI), no nordeste do Brasil. Inicialmente, foi realizada uma revisão sistemática sobre a qualidade dos estudos que envolvem o papel do farmacêutico na identificação de IM em hospitais, a partir da busca nos bancos de dados eletrônicos, janeiro de 1960 a agosto de 2010. A revisão utilizou como critérios de inclusão: (i) estudos realizados em hospitais; (ii) identificação de IM com a participação do farmacêutico; (ii) texto em língua inglesa. Em seguida, foi realizado um estudo longitudinal, na UTI, em um hospital privado do município de Aracaju-SE, entre 2008 e 2009, no qual foi identificada a prevalência e relevância clínica das IM do tipo fármaco-fármaco. Durante o estudo foram realizadas intervenções farmacêuticas que visavam o manejo da IM. Na revisão sistemática, apenas seis artigos atenderam a todos os critérios de inclusão específicos e o tamanho das amostras variou de 200 a 1785 pacientes. Quanto ao estudo longitudinal, foram coletadas 6.085 prescrições, sendo que 213 continham IM clinicamente relevantes. Destas 178 apresentaram severidade moderada e 35grave. As intervenções da farmácia clínica consistiram na elaboração de laudos para os médicos, que possibilitaram a redução de 40% de todas as interações. Os dados obtidos permitem inferir que a participação do farmacêutico clínico na identificação e manejo de IM, pode ter sido essencial para promover a segurança de pacientes da UTI.

Rotas sintéticas foram empregadas no grupo funcional ligado ao carbono 4 da trans-hidroxi-L-prolina para a obtenção de quatro análogos de prolina com amino e guanido grupos nesta posição e isomeria espacial cis e trans. Adicionalmente, o aminoácido guanidino fenilalanina foi comparado com os análogos de prolina em todos os ensaios realizados. Entre os análogos de prolina sintetizados, o peptídeo contendo o aminoácido não natural com o grupo funcional guanido e isomeria trans apresentou a melhor atividade inibitória contra trombina. Entretanto, o peptídeo sintetizado com o aminoácido guanidino fenilalanina ainda demonstra ter uma melhor atividade inibitória em comparação com os análogos de prolina. / Synthetic routes were employed in the functional group attached to the carbon 4 of trans-4-hydroxy-L-proline to obtain four proline analogues with amino and guanido groups in this position and cis and trans spatial isomerism. Additionally, the amino acid guanidino phenylalanine was compared with the analogues of proline in all tests. Among the proline analogues synthesized, the peptide containing the unnatural amino acid functional group with guanido and trans isomerism showed the best inhibitory activity against thrombin. However, the peptide synthesized with the amino acid guanidino phenylalanine exhibits an even better inhibitory activity in comparison to proline analogues.

Objective: The aim was to summarize the clinical literature on interactions between common illicit drugs and prescription therapies. Methods: Medline, Iowa Drug Information Service, International Pharmaceutical Abstracts, EBSCO Academic Search Premier, and Google Scholar were searched from date of origin of database to March 2011. Search terms were cocaine, marijuana, cannabis, methamphetamine, amphetamine, ecstasy, N-methyl-3,4- methylenedioxymethamphetamine, methylenedioxymethamphetamine, heroin, gamma-hydroxybutyrate, sodium oxybate, and combined with interactions, drug interactions, and drugdrug interactions. This review focuses on established clinical evidence. All applicable full-text English language articles and abstracts found were evaluated and included in the review as appropriate. Results: The interactions of illicit drugs with prescription therapies have the ability to potentiate or attenuate the effects of both the illicit agent and/or the prescription therapeutic agent, which can lead to toxic effects or a reduction in the prescription agent's therapeutic activity. Most texts and databases focus on theoretical or probable interactions due to the kinetic properties of the drugs and do not fully explore the pharmacodynamic and clinical implications of these interactions. Clinical trials with coadministration of illicit drugs and prescription drugs are discussed along with case reports that demonstrate a potential interaction between agents. The illicit drugs discussed are cocaine, marijuana, amphetamines, methylenedioxymethamphetamine, heroin, and sodium oxybate. Conclusion: Although the use of illicit drugs is widespread, there are little experimental or clinical data regarding the effects of these agents on common prescription therapies. Scientific Significance: Potential drug interactions between illicit drugs and prescription drugs are described and evaluated on the Drug Interaction Probability Scale by Horn and Hansten.

The aryl hydrocarbon receptor is a ligand-activated transcription factor that is involved in many important functions in the body. To study the role and function of AHR, an abundant amount of in vitro expressed and purified protein is needed. A baculovirus insect expression system is commonly employed to express AHR, however, there are several drawbacks with this method, such as mutation potential and high cost. A better in overexpression system is needed and we hypothesize that Pichia pastoris, a yeast expression system, could stably express AHR and ARNT (aryl hydrocarbon receptor nuclear translocator) in sufficient amount with reasonable cost. Codon optimized human AHR and ARNT genes were separately transformed into the Pichia pastoris genome and expressed. Co-immunoprecipitation, gel-shift assay and western analysis indicate Pichia pastoris was able to stably overexpress functional AHR and ARNT proteins in comparable yield and lower cost compared to baculovirus insect expression system and the expressed proteins were used to develop a new in vitro method to study AHR and ARNT binding. Pharmacokinetic studies were performed to investigate the role of AHR in rutacarpine-caffeine interactions. Oral RUT pretreatment was shown to reduce oral caffeine area under the curve (AUC) in rats, due to an increase in caffeine clearance (CL) and a decrease in oral bioavailability (F). RUT, an AHR ligand, increases caffeine CL by inducing Cyp1A2 enzyme, but the mechanism by which RUT reduces caffeine F is not understood. We hypothesize that it is also mediated via AHR pathway. To test the hypothesis, wild type (WT) and AHR knock out (KO) mice were administered caffeine IV and orally, with and without VEH or RUT pretreatment. As expected, PK data show higher caffeine CL and lower F values in WT, but similar CL and F values in AHR KO mice, upon RUT co-administration. Rats study, in which with pretreatment of vehicle, AHR ligands: RUT, beta-naphthoflavone or indole-3-carbinol before caffeine was dosed orally is consistent with mice study, that all three AHR agonists tested were able to reduce oral caffeine AUCs in rats. RUT reduces caffeine’s oral bioavailability is through AHR signaling pathway, however, However, the mechanism by which AHR mediates the reduced caffeine F is not known.