Benznidazole (BNZ) is traditionally used to treat Chagas disease. Despite its common use, BNZ has a poor water solubility and a variable bioavailability. The purpose of this study was to prepare BNZ microcrystals by solvent change precipitation and to study the effects of BNZ micronisation on therapeutic efficiency using a murine model of Chagas disease. The solvent change precipitation procedure was optimised in order to obtain stable and homogeneous particles with a small particle size, high yield and fast dissolution rate. The thermal and crystallographic analysis showed no polymorphic change in the microcrystals, and microscopy confirmed a significant reduction in particle size. A marked improvement in the drug dissolution rate was observed for micronised BNZ particles and BNZ tablets in comparison with untreated BNZ and commercial Rochagan. In vivo studies showed a significant increase in the therapeutic efficacy of the BNZ microparticles, corroborating the dissolution results.

Recebido em 5/1/10; aceito em 18/4/10; publicado na web em 9/8/10 PHYSICOCHEMICAL CHARACTERIZATION OF ANTICHAGASIC BENZNIDAZOLE. Currently, benznidazole (BNZ) is a unique therapeutic alternative available in Brazil to treat Chagas disease. Despite its traditional medical use, little is known about the chemical nature of this drug. A detailed study of the physicochemical properties of BNZ was performed using multiple assays. Thermal, diffractometric, morphological and reological drug profiles were obtained. The partition coefficient and solubility results allowed this drug to be classified as a class IV drug according to the biopharmaceutical classification system. This information will be useful for the development of more effective BNZ formulations and for establishing the quality profile of BNZ.Keywords: benznidazole; preformulation; biopharmaceutical classification. INTRODUÇÃOA pesquisa e o desenvolvimento de medicamentos inovadores têm sido uma empreitada cada vez mais cara e complexa, o que torna mais escassa a introdução de novas moléculas no mercado. Estima-se que de cada 30.000 compostos sintetizados, apenas 0,003% chegam a se tornar fármacos disponíveis no comércio. 2Dentre as causas que explicam estes inúmeros fracassos estão problemas derivados de sua biodisponibilidade e toxicidade, que podem estar relacionados ao escasso conhecimento acerca da natureza da molécula em estudo. 3Neste contexto, os estudos de pré-formulação, realizados nas etapas de pesquisa pré-clínica e clínica de fármacos inovadores, e que visam acumular o máximo de informação sobre o comportamento das novas entidades químicas, constituem um valioso instrumento para traçar estratégias de desenvolvimento racional de formulações mais eficazes e seguras e, portanto, com maiores possibilidades de êxito. 4,5 Diversos aspectos concernentes à substância ativa, como a biodisponibilidade a partir da forma farmacêutica, ou ao medicamento, como seu prazo de validade, e até mesmo seu processamento industrial são afetados pelas propriedades físico-químicas dos fármacos.O Benznidazol [BNZ] (N-benzyl-2-nitro-1-imidazole-acetamide) (Figura 1), constitui um dos únicos recursos terapêuticos disponíveis no combate à doença de Chagas há décadas. Este medicamento é bastante efetivo na fase aguda da doença, mas existem relatos de baixa ou nenhuma eficácia na fase crônica. Efeitos secundários severos associados à utilização desse fármaco têm sido reportados, tendo como consequência, a interrupção do tratamento medicamentoso. Apesar de ser um fármaco já consolidado no mercado e bastante estudado do ponto de vista farmacológico, as propriedades físico-químicas do BNZ são praticamente desconhecidas. Estudos de pré-formulação poderiam propiciar uma maior compreensão das suas características biofarmacêuticas e permitir vislumbrar alternativas para melhorar sua ação terapêutica.Desta forma, o objetivo deste estudo foi traçar o perfil físico-químico do BNZ através de diferentes ensaios de caracterização, como forma de estabelecer parâmetros de qualidade para est...

Effervescent tablets produced using an inclusion complex of BNZ with CD suggest a possible improvement in the bioavailability of BNZ, and this could represent a relevant advance in Chagas therapy.

Benznidazole (BNZ) is the primary chemotherapeutic agent for treating Chagas' disease; however, its poor water solubility and irregular oral absorption lead to the treatment failure in the chronic phase. The aim of this work was to investigate the utility of the polymer hydroxypropyl methylcellulose (HPMC) in controlling the release of BNZ from solid inclusion complexes with cyclodextrin to overcome the problem of its bioavailability. Preliminary studies of solubility were conducted in solution using selected β-cyclodextrin derivatives according to an experimental mixture design. The best cyclodextrin composition was used to produce solid-state systems by kneading in the presence or absence of HPMC. The formulations were characterized by different physico-chemical techniques, including the dissolution rate. Hydroxypropyl-β-cyclodextrin (HPβCD) produced the greatest improvement in drug solubility and was selected for the development of solid systems. Assays confirmed the production of true inclusion complexes between BNZ and HPβCD. The dissolution rate of the BNZ-HPβCD system was markedly increased, while the presence of HPMC retarded drug release. An optimal formulation obtained by the combination of kneading systems developed in appropriate ratios could be a promising drug delivery system with a prolonged therapeutic effect coupled with more balanced bioavailability. The produced systems present interesting perspectives for Chagas' therapy.

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