Assessment of acute oral and dermal toxicity of 2 ethyl-carbamates with activity against Rhipicephalus microplus in rats.

The acute oral and dermal toxicity of two new ethyl-carbamates (ethyl-4-bromophenyl-carbamate and ethyl-4-chlorophenyl-carbamate) with ixodicide activity was determined in rats. The oral LD50 of each carbamate was 300 to 2000 mg/kg, and the dermal LD50 of each carbamate was >5000 mg/kg. Clinically, the surviving rats that had received oral doses of each carbamate showed decreased weight gain (P < 0.05) and had slight nervous system manifestations. These clinical signs were evident from the 300 mg/kg dose and were reversible, whereas the 2000 mg/kg dose caused severe damage and either caused their death or was motive for euthanasia. At necropsy, these rats had dilated stomachs and cecums with diffuse congestion, as well as moderate congestion of the liver. Histologically, the liver showed slight degenerative lesions, binucleated hepatocytes, focal coagulative necrosis, and congestion areas; the severity of the lesions increased with dosage. Furthermore, an slight increase in gamma-glutamyltransferase, lactate dehydrogenase, and creatinine was observed in the plasma. The dermal application of the maximum dose (5000 mg/kg) of each carbamate did not cause clinical manifestations or liver and skin alterations. This finding demonstrates that the carbamates under study have a low oral hazard and low acute dermal toxicity.

Subchronic toxicity study in rats of two new ethyl-carbamates with ixodicidal activity.

Female and male Wistar rats were used to determine the subchronic oral toxicities of two new ethyl-carbamates with ixodicidal activities (ethyl-4-bromphenyl-carbamate and ethyl-4-chlorphenyl-carbamate). The evaluated carbamates were administered in the drinking water (12.5, 25 and 50 mg/kg/day) for 90 days. Exposure to the evaluated carbamates did not cause mortality or clinical signs and did not affect food consumption or weight gain. However, exposure to these carbamates produced alterations in water consumption, hematocrit, percentages of reticulocytes, plasma proteins, some biochemical parameters (aspartate aminotransferase, gamma-glutamyl transpeptidase, cholinesterase, and creatinine activities), thiobarbituric acid reactive substances, and the relative weight of the spleen. Histologically, slight pathological alterations were found in the liver that were consistent with the observed biochemical alterations. The nonobserved adverse effect levels (NOAELs) of the evaluated carbamates were 12.5 mg/kg/day for both the female and male rats. The low severity and reversibility of the majority of the observed alterations suggest that the evaluated carbamates have low subchronic toxicity.

Microagujas y Transcutol® como promotores de la penetración transdérmica de sibutramina formulada en parche transdérmico / Microneedles and Transcutol® as transdermal penetration enhancers of sibutramine formulated in a transdermal patch

Introducción: la principal barrera de permeación que tenemos es la piel. A pesar de ser una barrera casi impermeable para la mayoría de sustancias, se han buscado maneras para mejorar su permeabilidad utilizando nuevas tecnologías como es el uso de microagujas o promotores químicos como el Transcutol®. Objetivo: desarrollar y caracterizar un parche transdérmico a base de clorhidrato de sibutramina como fármaco modelo, usando Transcutol® y microagujas como agentes promotores de la penetración transdérmica. Métodos: se realizó la caracterización fisicoquímica de los parches mediante estudios de microscopia con luz polarizada, estudios de bioadhesión y resistencia a la ruptura. Los estudios de difusión se efectuaron en celdas de difusión verticales tipo Franz, utilizando piel abdominal humana como membrana entre ambos compartimentos. La cuantificación del principio activo se realizó mediante electroforesis capilar. Resultados: se obtuvieron parches bioadhesivos, con una adecuada estabilidad del activo en la matriz polimérica de quitosán al no precipitarse. El uso de Transcutol® y microagujas incrementó el paso de clorhidrato de sibutramina a través de piel humana con respecto al parche control. Se obtuvieron valores de flujo de 0,0649 mg.cm-2.h-1 y 0,0816 mg.cm-2.h-1 en el parche con agente promotor y microagujas de 1 y 2 mm respectivamente, en comparación con los valores de flujo de 0,0527 mg.cm-2.h-1 y 0,0554 mg.cm-2.h-1 para el parche sin agente promotor (control) utilizando microagujas de 1 y 2 mm respectivamente. Conclusiones: los resultados ponen de manifiesto la posibilidad de usar Transcutol® y microagujas para incrementar el paso de fármacos potentes y con estructura similar a la sibutramina por vía transdérmica, lo que genera de esta manera nuevas alternativas a las formas farmacéuticas orales para el tratamiento de padecimientos y enfermedades(AU)

Introduction: the main permeation barrier is the skin. Although it is almost an impermeable barrier to most substances, new ways have been examined to improve its permeability by using new technologies such as microneedles and chemical enhancers like Transcutol®. Objective: to develop and to characterize a transdermal patch containing sibutramine hydrochloride as model drug and using microneedles and Transcutol® as transdermal drug delivery enhancers. Methods: Physicochemical characterization of sibutramine hydrochloride patches using polarized light microscopy, bioadhesion, tensile strength studies. The diffusion studies were performed in Franz-type diffusion cells with human abdominal skin as a sort of membrane between both compartments. The active ingredient was quantified through capillary electrophoresis. Results: bioadhesive patches were obtained, with adequate stability of sibutramine hydrochloride in the polymer matrix of chitosan. The use of microneedles and Transcutol® increased sibutramine hydrochloride delivery through the human skin when compared with the control patch. The flow rates were 0.0649 mg.cm-2.h-1 and 0,0816 mg.cm-2.h-1 in the enhanced patch by using 1 and 2 mm microneedles respectively, in comparison with flow rates of 0,0527 mg.cm-2.h-1 and 0.0554 mg.cm-2.h-1 for the control patch having no enhancing agent with 1 and 2 mm microneedles respectively. Conclusions: the results show that it is possible to use Transcutol® and microneedles to increase the delivery of potent drugs having a structure similar to that of sibutramine through transdermal administration. All this generates new alternatives to oral pharmaceuticals in order to treat ailments and diseases(AU)