The influence of gastrointestinal parasitism on fecal elimination of doramectin, in lambs.

Abstract A study was done to investigate the effect of parasitism on patterns of doramectin (DRM) fecal elimination in lambs. Fourteen Suffolk Down parasitized lambs (26.9±1.5 kg body weight: bw) were purposely selected for the study. Seven pairs of lambs were allocated into two experimental groups. Group I (non-parasitized) was pre-treated with 3 repeated administrations of 5 mg/kg bw of fenbendazole to maintain a non-parasitized condition. In Group II (parasitized), the lambs did not receive any anthelmintic treatment. After 85 d of the pre-treatment period, both groups were treated with a subcutaneous injection of 200 μg/kg bw of DRM. Fecal samples were collected at different times between −85 d before and 60 d after the DRM treatment, for both parasitological and chromatographic analysis. Samples were analyzed by high-performance liquid chromatography (HPLC) with fluorescence detection. Data of DRM concentrations were expressed as wet weight. A non-linear pharmacokinetic analysis was performed and results were compared using the Mann Whitney test. Fecal maximum concentrations ( C max ) of DRM were 1.37±0.19 μg/g (parasitized group) and 0.86±0.15 μg/g (non-parasitized group) observed at the time of the maximum concentration ( T max ) of 2.1±0.4 and 3.1±0.3 d, respectively. Differences in C max values were significant ( P