Residue depletion of lincomycin hydrochloride-spectinomycin sulfate injection in pigs

【Objective】The residue depletion of lincomycin hydrochloride-spectinomycin sulfate injection in pigs was investigated in this study, and its withdrawal time was estimated. 【Method】 In routine breeding conditions, thirty healthy pigs were randomly allocated to six treatment groups. All of them were treated with lincomycin hydrochloride-spectinomycin sulfate injection at a dosage of 15 mg/kg (5 mg lincomycin and 10 mg spectinomycin) once daily for 5 consecutive days. Five medicated pigs were slaughtered at 8, 24, 72, 144, 240 and 336 h after intramuscular administration, and muscle, liver, kidney, fat and injection site tissues were sampled. The tissue concentration of lincomycin and spectinomycin was analyzed respectively by liquid chromatography-mass spsectrometry (LC-MS/MS) and high-performance liquid chromatography (HPLC). 【Result and conclusion】 At 6 days postmedication, all observations of spectinomycin and lincomycin were below the corresponding MRLs. In all of the detected tissues, kidney had the highest drug concentration followed by liver, injection site, muscle and fat with the lowest drug concentration, indicating that kidney was target tissue for spectinomycin and lincomycin. Based on the MRLs, which were established by the Chinese Agriculture Ministry, the withdrawal time in pigs was analyzed by WT1.4 software. The results indicated that the withdrawal time of lincomycin hydrochloride-spectinomycin sulfate injection should be 8 days after intramuscular administration of 15 mg/kg in pigs.