Propafenone is a new class 1C antiarrhythmic agent with additional calcium antagonistic and beta-blocking activities. Clinically it is effective in the treatment of supraventricular and ventricular tachycardia, atrial and ventricular fibrillation, ventricular premature contractions and for the management of Wolf-Parkinson-White syndrome. In North America it is still an investigational drug. Propafenone is a chiral drug and is used clinically in the racemic form. The enantiomers of numerous chiral drugs have been shown to differ in their disposition kinetics in the body due to their stereoselective pharmacokinetics and/or pharmacodynamic properties. Two enantiomers are thus often considered as two different entities. The relative antiarrhythmic activities of individual enantiomers of propafenone have not been studied, nor their pharmacokinetic parameters have been elucidated. In order to study the possible enantioselective role of propafenone in the body, a stereoselective assay method would be required. The present study describes the development of a sensitive and stereoselective chromatographic assay method for the simultaneous determination of the two enantiomers of propafenone in human plasma. Attempts for direct separation of the enantiomers of propafenone included several GLC and HPLC chiral stationary phases. The chiral stationary phases were a Chirasil-Valʳ GLC stationary phase, a Pirkle 2,4 dinitro-(D)-phenylglycine HPLC stationary phase and a β-cyclodextrin HPLC stationary phase. Unfortunately, these did not resolve the enantiomers of propafenone. Formation of the diastereomers with R(+)-⍺-methyl benzyl isocyanate and racemic propafenone were partially resolved on a reverse phase HPLC using a 5 u, 25 x 0.45 cm i.d. ODS column and methanol/water (70:30) as the mobile phase. However, due to the long retention time (42 min), incomplete resolution (RS=1.15) and poor sensitivity for detection (500 ng of each enantiomer injected) this method was not deemed suitable for the pharmacokinetic studies planned, since the therapeutic plasma concentration range of propafenone is 64-1044 ng/mL. The second chiral derivatizing reagent, 2,3,4,6-tetra-0-acetyl-β-D-glucopyranosylisothiocyanate (GITC), was synthesized in our laboratory. This reagent gave better resolution of the enantiomers (RS=1.4) within 15 minutes with enhanced sensitivity for detection (150 ng of each enantiomer injected). To further optimize the limit of detection for future pharmacokinetic studies of propafenone, R(-)-1 -(naphthyl) ethylisocyanate, a chiral derivatizing agent, was employed. This reagent reacted with racemic propafenone and permitted the resolution of both enantiomers within 24 minutes (R5=l.25) and the minimum level of detection was 100 ng (at the detector) for each enantiomer of propafenone. Using this method, linearity was established over the concentration range, 125-1000 ng for each enantiomer (injected) with a coefficient of determination (r²) of greater than 0.99. Reproducibility and precision of this assay method was obtained with an average coefficient of variability of 4.5% for the R(-) enantiomer and 7.2% for S(+) enantiomer at concentrations of 125-1000 ng/mL. Below the lower quantity, the NEIC-propafenone reaction virtually stopped at the conditions set for derivatization. A similar lack of reactivity at low concentrations was also observed with the GITC-propafenone reaction. The absence of an autocatalysing effect of propafenone at lower nanogram levels, as well as two possible conformational forms of propafenone were also investigated. The existence of two conformational isomers of propafenone, due to intramolecular hydrogen bonding in aprotic solvents, was chromatographically verified. In addition, chromatographic separation of all the proposed conformers was obtained, indicating that enantiomeric separation and quantitation of propafenone enantiomers as their urea derivatives is substantially hindered. To eliminate hydrogen bonding interactions, the carbonyl group of propafenone was blocked with dansylhydrazine and subsequently derivatized with the chiral R(-)NEIC reagent. The HPLC resolution (RS=1.35) of this dual derivative was better than that using the R(-) NEIC reagent alone, and the minimum level of detection was 2.5 ng for each enantiomer. Unfortunately, this procedure still did not provide adequate assay precision and accuracy at the lower levels required for single dose pharmacokinetic studies. / Pharmaceutical Sciences, Faculty of / Graduate

No description available.

An accurate plasma concentration-response relationship for propafenone (PF), a potent class 1 antiarrhythmic agent, has not yet been defined. A general pharmacological premise suggests that only the free drug is available to contribute to the observed pharmacological response. It has previously been shown that PF is highly bound to α-l-acid glycoprotein (AAG) which results in a low free PF concentration. The correlation of free PF concentration and response failed to adequately describe the dose response relationship. It has subsequently been shown that upon chronic dosing, two active metabolites, namely 5-hydroxypropafenone (5-OH-PF), and n-depropylpropafenone (n-depropyl-PF) accumulate in humans treated with PF. It is highly likely that the free concentration of PF, in addition to those of 5-OH-PF and n-depropyl-PF, contributes to the observed pharmacological effect following administration of PF at steady-state. To date, no accurate estimation of 5-OH-PF binding in serum has been established. This thesis examines the binding characteristics of PF and 5-OH-PF and their interaction in human serum, and in solutions of AAG, human serum albumin (HSA), high density lipoproteins (HDL), low density lipoproteins (LDL), and very low density lipoproteins (VLDL) using equilibrium dialysis. The binding of PF (2.0 μg/mL) and 5-OH-PF (0.5 μg/mL) was examined in serum when both drug and metabolite were present. The free fraction (FF) of PF and 5-OH-PF in serum was 0.063 ± 0.004 and 0.232 ± 0.020, respectively. Both PF and 5-0H-PF were found to bind to a high affinity, low capacity binding site on AAG, in addition PF showed a second low affinity, high capacity binding site. PF displayed a 10 fold greater affinity for the high affinity binding site on AAG when compared to 5-OH-PF. Both PF and 5-OH-PF showed only one low affinity, high capacity site on HSA of similar affinity. The interaction of PF and 5-OH-PF with HDL, LDL, and VLDL appeared to be due to solubilization, rather than a "true" drug-protein binding interaction, since it correlated well with the concentration of cholesterol within the lipoprotein complex (PF, r²=0.85; 5-OH-PF, r²=0.96). However, PF appeared to show saturable binding to the HDL complex. The uptake of PF and 5-OH-PF was greatest in LDL followed by HDL, and finally VLDL. In serum PF displayed both a high affinity, low capacity, and a low affinity, high capacity binding sites, although a similar observation was expected for 5-OH-PF, only one binding site could be experimentally identified. The uptake of 5-OH-PF by red blood cells (RBC) appeared to be approximately 5 fold greater than that of PF (i.e. The ratio of PF and 5-OH-PF concentration in the red blood cell/plasma was 0.7 ± 0.1 and 3.2 ± 0.5, respectively). When the binding of PF and 5-OH-PF was considered separately, the binding profiles were similar, that is, both drugs showed high affinity binding to AAG, and low affinity binding and/or non-specific binding to other serum proteins such as HSA, HDL, LDL, and VLDL. However, when both drug and metabolite were present, the binding of 5-OH-PF to AAG was found to be reduced. This is thought to occur as a result of the displacement of 5-OH-PF by PF from AAG. Thus, the binding of 5-OH-PF was noted to be more dependent on HSA, and lipoproteins when compared to PF. On the other hand, the binding of PF (2.0 μg/mL), even with the addition of 5-OH-PF, was dependent largely on the concentration of AAG. Although the binding of 5-OH-PF was apparently not altered by the addition of PF in serum, a decrease in the binding of 5-OH-PF by the addition of PF was observed. It is hoped that the understanding gained from this thesis will provide information regarding the relative importance of free PF and 5-OH-PF plasma concentration in future pharmacodynamic studies of PF. / Pharmaceutical Sciences, Faculty of / Graduate

No contexto de qualidade, segurança e eficácia dos medicamentos, os produtos de degradação surgem com um crescente foco regulatório no Brasil e no mundo. Para análise confiável dos medicamentos, métodos indicativos de estabilidade devem ser utilizados, visando a avaliação qualitativa e quantitativa das impurezas e dos produtos de degradação neles contidos. O cloridrato de propafenona é utilizado no tratamento de arritmias supraventriculares e ventriculares, apresentando-se como bloqueadores dos canais de sódio, além de ser um betabloqueador. O cloridrato de pioglitazona é um agente anti-hiperglicemiante que atua primariamente diminuindo a resistência à insulina, no tratamento da Diabetes tipo 2. Os métodos oficiais descritos nas farmacopeias, muitas vezes, não fornecem informações a respeito de análise de impurezas farmacêuticas e de produtos de degradação. Assim sendo, deve-se verificar se os métodos são indicativos da estabilidade, antes de utilizá-los para analisar os produtos de degradação. A presente pesquisa tem como objetivo avaliar amostras simuladas dos medicamentos citados, após serem submetidos a condições de estresse; determinar os principais produtos de degradação através dos métodos descritos na Farmacopeia Americana e avaliar se tais métodos são indicativos de estabilidade, assim como realizar balanço de massa. Foi realizado um delineamento fatorial 32 dos meios de degradação avaliando-se a variação do tempo e da intensidade e a capacidade de detecção e quantificação de produtos de degradação presentes. Os fatores considerados no delineamento foram degradação ácida, alcalina, meio oxidativo com peróxido de hidrogênio, e temperatura/umidade além da fotoestabilidade. O cloridrato de propafenona apresentou degradação nos estresses ácidos, oxidativos e em temperatura/umidade. No meio alcalino e a exposição a luz (branca/UV), a magnitude da degradação foi amena. Houve um balanço de massas entre os métodos de doseamento e de impurezas, mostrando-se que o método é indicativo de estabilidade. O principal produto de degradação, no meio ácido e oxidativo, foi identificado utilizando o método de LC-MS. O cloridrato de pioglitazona apresentou degradação em meios básicos, oxidativos assim como em exposição à luz e elevada temperatura/umidade. A hidrólise ácida não apresentou impacto significativo. Os métodos de doseamento e de impurezas não apresentaram balanço de massa, mostrando-se que o método não é indicativo de estabilidade. As análises in silico, com o software Zeneth®, foi utilizada para estabelecer correlações entre o processo de degradação e os plausíveis produtos formados. Assim, conclui-se que os dados de estresses obtidos, neste trabalho, podem servir como suporte nos estudos de estabilidade, bem como contribuir na definição das condições de transporte e armazenamento do cloridrato de propafenona e cloridrato de pioglitazona. / In the context of quality, safety and efficacy of pharmaceuticals, degradation products ascend with a growing regulatory focus in Brazil and in the world. For reliable analysis of pharmaceutical products, stability indicative methods must be used, aiming at qualitative and quantitative analysis of impurities and degradation products contained therein. Propafenone HCl is used in the treatment of supraventricular and ventricular arrhythmias and has sodium channel blocking capacity, besides its betareceptor blocking activity. Pioglitazone HCl is an anti-hiperglicemiante agent that acts primarily by reducing insulin resistance in the treatment of type 2 diabetes. The official methods described in the Pharmacopoeias often do not provide information regarding the analysis of pharmaceutical impurities and degradation products. Therefore, it important to verified whether the methods are stability indicative or not, before being use in the analysis of degradation products. The objective of this research is to evaluate simulated samples of cited pharmaceuticals, after submission to stress conditions. To determine the main degradation products through the methods described in the American Pharmacopoeia and assess whether such methods are indicative of stability by mass balance approach. A factorial design (32) of the degradation mediums was carried out to evaluate impact of time of contact and variable intensity. On the outer side, the ability of the method to detect and quantify degradation products was also assessed. The degradation medium factors considered in the design were, acid, alkaline, oxidant medium using hydrogen peroxide, temperature/humidity and photostability. Propafenone hydrochloride presented degradation in acid, oxidative and temperature/humidity stress conditions. In the alkaline medium and exposure to light (white/UV), the extent of degradation was mild. There was a mass balance between the assay method and impurity method, illustrating that the method is stability indicative. The main degradation product, in the acidic and oxidative medium, was identified using the LC-MS method. Pioglitazone hydrochloride presented degradation in basic, oxidative means as well as on exposure to light and elevated temperature/humidity conditions. Acidic hydrolysis has no significant impact. The assay and impurity methods did not show mass balance, elucidating that the method is not stability indicative. In silico analysis, with the Zeneth® software, was used to establish correlations between the degradation process and the plausible degradation pathway and products. Thus, it is concluded that the data obtained in degradation studies, in this work, may serve as support in the stability studies, as well as subsidize to define transport and storage conditions for propafenone HCl and pioglitazone HCl.

No contexto de qualidade, segurança e eficácia dos medicamentos, os produtos de degradação surgem com um crescente foco regulatório no Brasil e no mundo. Para análise confiável dos medicamentos, métodos indicativos de estabilidade devem ser utilizados, visando a avaliação qualitativa e quantitativa das impurezas e dos produtos de degradação neles contidos. O cloridrato de propafenona é utilizado no tratamento de arritmias supraventriculares e ventriculares, apresentando-se como bloqueadores dos canais de sódio, além de ser um betabloqueador. O cloridrato de pioglitazona é um agente anti-hiperglicemiante que atua primariamente diminuindo a resistência à insulina, no tratamento da Diabetes tipo 2. Os métodos oficiais descritos nas farmacopeias, muitas vezes, não fornecem informações a respeito de análise de impurezas farmacêuticas e de produtos de degradação. Assim sendo, deve-se verificar se os métodos são indicativos da estabilidade, antes de utilizá-los para analisar os produtos de degradação. A presente pesquisa tem como objetivo avaliar amostras simuladas dos medicamentos citados, após serem submetidos a condições de estresse; determinar os principais produtos de degradação através dos métodos descritos na Farmacopeia Americana e avaliar se tais métodos são indicativos de estabilidade, assim como realizar balanço de massa. Foi realizado um delineamento fatorial 32 dos meios de degradação avaliando-se a variação do tempo e da intensidade e a capacidade de detecção e quantificação de produtos de degradação presentes. Os fatores considerados no delineamento foram degradação ácida, alcalina, meio oxidativo com peróxido de hidrogênio, e temperatura/umidade além da fotoestabilidade. O cloridrato de propafenona apresentou degradação nos estresses ácidos, oxidativos e em temperatura/umidade. No meio alcalino e a exposição a luz (branca/UV), a magnitude da degradação foi amena. Houve um balanço de massas entre os métodos de doseamento e de impurezas, mostrando-se que o método é indicativo de estabilidade. O principal produto de degradação, no meio ácido e oxidativo, foi identificado utilizando o método de LC-MS. O cloridrato de pioglitazona apresentou degradação em meios básicos, oxidativos assim como em exposição à luz e elevada temperatura/umidade. A hidrólise ácida não apresentou impacto significativo. Os métodos de doseamento e de impurezas não apresentaram balanço de massa, mostrando-se que o método não é indicativo de estabilidade. As análises in silico, com o software Zeneth®, foi utilizada para estabelecer correlações entre o processo de degradação e os plausíveis produtos formados. Assim, conclui-se que os dados de estresses obtidos, neste trabalho, podem servir como suporte nos estudos de estabilidade, bem como contribuir na definição das condições de transporte e armazenamento do cloridrato de propafenona e cloridrato de pioglitazona. / In the context of quality, safety and efficacy of pharmaceuticals, degradation products ascend with a growing regulatory focus in Brazil and in the world. For reliable analysis of pharmaceutical products, stability indicative methods must be used, aiming at qualitative and quantitative analysis of impurities and degradation products contained therein. Propafenone HCl is used in the treatment of supraventricular and ventricular arrhythmias and has sodium channel blocking capacity, besides its betareceptor blocking activity. Pioglitazone HCl is an anti-hiperglicemiante agent that acts primarily by reducing insulin resistance in the treatment of type 2 diabetes. The official methods described in the Pharmacopoeias often do not provide information regarding the analysis of pharmaceutical impurities and degradation products. Therefore, it important to verified whether the methods are stability indicative or not, before being use in the analysis of degradation products. The objective of this research is to evaluate simulated samples of cited pharmaceuticals, after submission to stress conditions. To determine the main degradation products through the methods described in the American Pharmacopoeia and assess whether such methods are indicative of stability by mass balance approach. A factorial design (32) of the degradation mediums was carried out to evaluate impact of time of contact and variable intensity. On the outer side, the ability of the method to detect and quantify degradation products was also assessed. The degradation medium factors considered in the design were, acid, alkaline, oxidant medium using hydrogen peroxide, temperature/humidity and photostability. Propafenone hydrochloride presented degradation in acid, oxidative and temperature/humidity stress conditions. In the alkaline medium and exposure to light (white/UV), the extent of degradation was mild. There was a mass balance between the assay method and impurity method, illustrating that the method is stability indicative. The main degradation product, in the acidic and oxidative medium, was identified using the LC-MS method. Pioglitazone hydrochloride presented degradation in basic, oxidative means as well as on exposure to light and elevated temperature/humidity conditions. Acidic hydrolysis has no significant impact. The assay and impurity methods did not show mass balance, elucidating that the method is not stability indicative. In silico analysis, with the Zeneth® software, was used to establish correlations between the degradation process and the plausible degradation pathway and products. Thus, it is concluded that the data obtained in degradation studies, in this work, may serve as support in the stability studies, as well as subsidize to define transport and storage conditions for propafenone HCl and pioglitazone HCl.