Withdrawal time of fosfomycin in pigs and broiler chickens after oral and intramuscular administration

Abstract

Fosfomycin (FOS) is a broad-spectrum bactericidal antibiotic, used for the treatment and prevention of pulmonary and enteric infections in poultry and intensive pig farming. FOS pharmacokinetics has been extensively studied in humans and animals; although its withdrawal time (WDT) has not been determined yet. This study was aimed to determine WDTs of calcium and disodium FOS in pigs and broiler chickens. For residue analysis and WDT calculation, 48 healthy, 145–150 day-old pigs and 48 healthy, 14 day-old, broiler chickens, were used. In both species, animals were divided in two groups (A and B). Groups A – Oral Assays: calcium FOS, 5 consecutive days; 30 mg/kg pv, (pigs) and 40 mg/kg pv (broiler chickens). On the fifth day of trial, FOS dosage was discontinued. Groups B – Intramuscular Assays: disodium FOS; 15 mg/kg pv (pigs) and 10 mg/kg pv (broiler chickens). In all assays, 24, 48, 72 and 96 h after dosage discontinuation, groups of 6 animals were euthanized. Samples of muscle, liver, kidney and skin-fat were obtained and processed for the determination of residual concentrations of FOS by HPLC MS–MS. WDTs were calculated by the statistical program WTM 1.4. The longer WDT were 2.95 and 2.55 days (kidney) for the oral administrations and 1.73 (liver) and 1.72 days (muscle), for the intramuscular administrations, in pigs and broiler chickens, respectively. Therefore, WDTs of 3 days (after oral administrations) and 2 days (after intramuscular administrations), could be assigned as a precautionary principle for public health, without a significant economic impact for the producers.