Abstract

Marbofloxacin, a second generation fluoroquinolone is active against Gram-negative, some Gram-positive and mycoplasma bacteria, it constitutes an alternative in aquaculture, as background in mammals indicates good oral absorption and broad tissue distribution. Because there are no studies in trout, this study aims to characterize its disposition in skin and muscle by oral application and withdrawal period in summer conditions. Rainbow trout (Oncorhynchus mykiss), randomly selected, weighty 326.3 ± 44.1 are given marbofloxacin 2 mg/kg orally. Serie 1 (n=42) with food and Serie 2 (n=42) fasting for 12 hours prior-administration and 3 hours post-administration. The animals placed in batches (n=3) in 500 liters of water at 19.3 ± 0.5 °C whit renewal rate of 2.2. At different times up to 120 hours post application each batch is euthanized by exsanguination extracting skin and muscle sample, that are then stored at -20 °C. Preparative assay consisted of liquid-liquid extraction of the analyte whit mcg of sample, 200 microliters water, 800 microliters solution of water: methanol: perchloric 50 :50 : 2 v/v/v and enrofloxacin as internal standard. Then it was centrifuged at 13.500 rpm 25´at 4 °C. Separation and quantification were done by HPLC by isocratic elution on reverse phase using C-18 column and a fluorescence detector at 295 nm excitation and 490 nm emission, mobile phase composed of water, acetronitrile and triethylamine (79: 19: 1 v/v/v) at pH 3. Average temporal concentrations are analyzed PK solution 2.0 software. Withdrawal period are established using residual values with WT 1.4 program with 95% confidence. The results indicate that the presence of food delays absorption and reduces tissue disposition and Cmáx, but provides greater permanence, reflected by the withdrawal period expressed in Acumulated Thermal Units (ATU) in muscle: 65.8 (fasting) and 95.9 (food) and skin: 149.04 (fasting) and 230.1 (food).