Determination of oxytetracycline residue in Cyprinus carpio of muscle and liver by HPLC method

Oxytetracycline (OTC) is the only form of tetracycline compounds which is approved by FDA to be used for prevention and treatment of aquatic animals’ diseases. The aim of this study was to determine the amount of OTC residue in muscle and liver of Common carp (Cyprinus carpio) by high performance liquid chromatography (HPLC) using single dose method. 12 fishes were divided into 4 treatments and each treatment was divided into 3 replicates. Regarding the weight range of fishes   ( 40-80 g ) and also the injectable OTC dosage rate of  25-50 mg/kg in accordance with aquatic animals pharmaceuticals ,0.04 ml of injectable solution of OTC was intramuscularly injected, then muscle and liver were sampled from fishes after 6, 24, 48 and 72 hours. Measurement of OTC residues was carried out by HPLC after solid phase extraction (SPE). The highest recorded concentrations in muscle and liver were observed in 6hr and 24hr after injection respectively (3.37μg/g and 17.37μg/g). The lowest concentrations in muscle and liver belonged to 72hr after injection (0.29μg/g and 9.52μg/g respectively). The results indicated that OTC concentrations descend in muscle from 6th to 72th hour. But in liver, because of OTC redistribution, drug concentration increases significantly after 24hr (P<0.05), then it decreases after 48 and 72hr.