Avalia??o da toxicidade aguda do antim?nio trivalente : formas livres ou lipossomal associadas ou n?o ? administra??o de ?cido asc?rbico.

Programa de P?s-Gradua??o em Ci?ncias Farmac?uticas. CIPHARMA, Escola de Farm?cia, Universidade Federal de Ouro Preto.Compostos antimoniais s?o utilizados no tratamento das Leishmanioses, por?m h? lacunas importantes a respeito dos seus mecanismos de a??o e toxicidade. Formula??es lipossomais foram desenvolvidas objetivando promover menor toxicidade e maior efic?cia desses compostos. Visando dar continuidade aos trabalhos anteriores de nosso grupo de pesquisa com o SbIII na forma lipossomal e com a potencial a??o cardioprotetora do ?cido asc?rbico (AA) quando associado ao SbIII, este trabalho avaliou a toxicidade aguda n?o cl?nica de duas formula??es lipossomais de SbIII, convencional (LCSbIII) e peguilada (LPSbIII) associadas ou n?o ? administra??o de AA, ap?s sua administra??o por via intraperitoneal (IP), em camundongos Swiss. As prepara??es lipossomais foram realizadas pelo m?todo de congelamento/descongelamento, seguido de extrus?o. Para quantifica??o do SbIII nessas formula??es realizou-se a revalida??o de um m?todo anal?tico por ICP-OES. O percentual de encapsula??o obtido foi de, aproximadamente, 15% para LCSbIII e de 14% para LPSbIII . Em m?dia, os tamanhos das part?culas foram de 170 a 230 nm, para ambas as formula??es, com ?ndice de polidispers?o inferior a 0,3. LPSbIII foi mais est?vel por 30 dias e apresentou perfil de libera??o in vitro mais lento. Para determina??o da dose limite (DL) de SbIII utilizou-se o m?todo do ?Teste de Doses Fixas? (TDF), no qual foram utilizadas as doses: 17, 18, 19 e 20 mg.kg-1. A dose ?nica de 18 mg.kg-1 (DL) de SbIII livre induziu claros sinais de toxicidade e altera??es histopatol?gicas qualitativas. No estudo de toxicidade aguda, as administra??es de SbIII livre e SbIII+AA induziram perda de peso corporal nos animais, mortalidade significativa e sinais cl?nicos de toxicidade, como: ataxia, piloere??o, tremores, convuls?es e elevados n?veis de ALT, AST e fosfatase alcalina. Nesses grupos, observou-se degenera??o celular, presen?a de pigmentos de hemossiderina e necrose tecidual no f?gado. Tamb?m foram observadas esclerose glomerular nos rins e necrose no ba?o. Em geral, os lipossomas reduziram a frequ?ncia e a intensidade dos sinais cl?nicos de toxicidade, al?m de n?o ter sido observada a presen?a de mortalidade. Les?es histol?gicas de maior gravidade tamb?m n?o foram observadas nos tratamentos lipossomais. Nos diferentes grupos estudados n?o foram observadas altera??es importantes nas an?lises de hem?cias, hemat?crito, mon?citos e neutr?filos. A associa??o da administra??o de AA com SbIII, nas formas livre ou lipossomais, n?o produziu efeito protetor em f?gado, ba?o e rins contra a toxicidade desse semimetal nas condi??es experimentais avaliadas. Por?m, os seus efeitos t?xicos foram reduzidos com a utiliza??o dos lipossomas convencionais e peguilados.Antimony compounds are used in the treatment of Leishmaniasis but there are important gaps concerning their mechanisms of action and toxicity. Liposomal formulations were developed aiming to promote greater efficiency and lower toxicity of these compounds. Aiming to continue the previous work of our research group with SbIII in liposomal form and the potential cardioprotective effect of ascorbic acid (AA) when associated SbIII, this study evaluated the non-clinical acute toxicity in two liposomal formulations of SbIII: conventional (CLSbIII) and PEGylated (PLSbIII), associated or not with administration of AA, after its administration intraperitoneally (IP) in Swiss mice. Liposomal preparations were performed by the freeze/thaw method followed by extrusion. For quantification of SbIII of these formulations, a revalidation of an analytical method by ICP-OES was carried. The percentage of encapsulation was obtained in approximately 15% and 14% for CLSbIII to PLSbIII, respectively. The average particle sizes were 170 at 230 nm for both formulations, with an index of polydispersity less than 0.3. PLSbIII was more stable for 30 days and showed in vitro release profile slower. To determine the limit dose (LD) of SbIII used the method "Test of fixed doses" (TFD) in which the doses were used: 17, 18, 19 and 20 mg.kg-1. A single dose of 18 mg.kg-1 (LD) free SbIII induced clear signs of toxicity and qualitative histopathological changes. In acute toxicity study, the administrations of free and SbIII and SbIII+AA induced weight loss in animals, significant mortality and clinical signs of toxicity, such as ataxia, piloerection, tremors, seizures and high levels of ALT, AST and alkaline phosphatase. In these groups, we observed a cell degeneration, the presence of hemosiderin pigment and liver necrosis. Glomerular sclerosis were also observed in the kidneys and also was spleen necrosis. In general, liposomes decreased the frequency and intensity of clinical toxicity signs, and the presence of mortality was not observed in mice treated with liposomes. More severe histological lesions were also not observed in liposomal treatments. In the different groups, significant alterations were observed in analysis of hematocrit, monocytes and neutrophils. The association with the administration of SbIII+AA, in free or liposomal form produced no protective effect in the liver, spleen and kidneys against this semi-metal toxicity in our experimental conditions. However, its toxic effects were minimized by the use of conventional and PEGylated liposomes