Abstract

Difloxacin (DFX) is a fluoroquinolone used only in domestic animals that develops bactericidal actions by selective blocking of the DNA-gyrase enzyme in G+, G- and mycoplasma microorganisms. The background of DFX in mammals indicates high tissue distribution. This study seeks to establish in broiler chickens, if plasma and tissue levels are equivalent and establish a withdrawal period (Pr) in different tissues. Chickens (n= 70) Cobb line, approximately 45 days old and 1.9 ± 0.2 kg weight, randomly selected from a stock of 1200 birds. 14 batches of 5 animals each were formed, who received an oral single dose of 20 mg/kg of DFX after fasting for 12 and 3 hours before and after application, respectively. Subsequently, each batch was sacrificed at pre-established times, samples of blood, by exanguination, and tissue samples were obtained until 120 hours post application. DFX was quantified by HPLC using C18 column, mobile phase consisting of water, acetonitrile and triethylamine (790: 200: 10 v/v/v) adjusted to pH 3.0 and fluorometer reading set at 295 nm excitation and 490 nm emission. In plasma and each tissue, DFX concentration averages by time were analyzed with the non-compartmental pharmacokinetic software PK Solution. Pr was estimated with the WT1.4 software, according to the 300 µg/kg MRL established for muscle, skin and lung of, 600 µg/kg for kidney and 1,900 µg/kg for liver. Due to its fat-soluble characteristics and poor plasma protein binding, difloxacin oral application experiences rapid absorption, high tissue distribution and prolonged permanence in the body, generates ratios in muscle, skin, liver, kidney and lung versus plasma of 3.9, 3.1, 32.8, 166.3 and 7.7, respectively and a Pr of 3 days for muscle, liver and skin and 5 days for kidney and lung, compatible with the productive cycles of broilers.