Fipronil injetável para bovinos: farmacocinética e eficácia no controle de Haematobia irritans e Dermatobia hominis

Abstract

Brazil is the country belonging to MERCOSUL with the largest cattle herd. It is the first in number of slaughter and meat production, therefore occupies a prominent place on the international scene. To maintain productivity is needed investments in management, genetics and sanities operations. When talk about sanities the parasitosis play a role of importance and may determine serious damage to health of animals. In the last three decades have not been a new development of molecules with fungicidal action only the introduce, in the veterinary market Brazilian products, innovations in associations, presentations, formulations, routes and forms of administration. The aim of this study is development an injectable formulation of fipronil and evaluate its bioavailability and efficacy to control Haematobia irritans e Dermatobia hominis. Thirteen formulations were developed (F1 to F13). It was performed accelerated stability test where after six months five formulations were stable (F3, F4, F5, F10 e F11). It studied the plasma profile of stable higher dosage formulations (F10 and F11) and compared with the topical commercial formulation. For the development of analytical methods, two sample preparation techniques were tested, both using HPLC-UV techniques. The use of RAM column was not efficient and the SPE technique was validated with a linear range of 5 to 500 ng / mL for fipronil and 10 a 500 ng / mL for fipronil sulfone. The precisions were 13.7 e 10.9 to fipronil and fipronil sulfone respectively and accuracy of 7.2 and 5.5% to fipronil and fipronil sulfone respectively. With this methodology it was possible to evaluate the plasma profile of the formulations F10, F11 and topical commercial formulation finding the higher bioavailability at injectable formulation with fewer N-metilpirrolidone (F10). The metabolism product, fipronil sulfone, was quantitated after approximately 15 days in all formulations and the half-life time of fipronil was 37 hours for injectable formulations (F10 e F11) and 100 hours for topical commercial formulation. To evaluate the influence of the formulations in the interruption of the life cycle of H.irritans was performed a efficacy test during 21 days. For this test was collected feces of treated animals. Faeces samples were incubated for evaluate of hatching eggs. The results show that F10 and F11 were able to inhibit the hatching eggs of H.irritans. To evaluate the efficacy to control D.hominis larvae was performed a efficacy test with 10 cattle during 28 days finding 54, 65 and 72% efficacy for commercial topical formulation, F10 and F11 respectively, 7 days after treatment. Twenty-one days after treatment, the efficacy increased to 97, 99 and 98% for F10, F11 and commercial topical formulation respectively demonstrating that the formulations were effective in controlling D.hominis in cattle. These results clearly demonstrate that subcutaneously fipronil action as a ectoparasiticide to control of these parasites in cattle and may be a new treatment alternative.