Kinetic analysis of oxytetracycline residues in Chinese mitten crab, Eriocheir sinensis, muscle following intramuscular administration

Crab culture is a very important economic industry in China. An epidemic of tremor disease of Chinese mitten crabs, Eriocheir sinensis, has become a serious problem in recent years. A spiroplasm has been proved to be the causative agent of this disease. Oxytetracycline (OTC) is used widely in aquaculture and was confirmed to be very effective against this pathogen. In this study, the distribution and depletion patterns of OTC in crab muscle were evaluated following single intramuscular doses of 2, 8 and 40 mg kg⁻¹ body weight. OTC was detected with a validated HPLC method. Concentration-time profiles were well described by a three-compartment model with first-order absorption after a single dose of 8 and 40 mg kg⁻¹. For comparison, a non-compartment model was employed. A withdrawal time of 48.29 and 55.92 days was suggested prior to consumption after receiving 8 and 40 mg kg⁻¹. A recommended therapeutic dose of OTC in theory was calculated to be 36.37 mg kg⁻¹. OTC was distributed well throughout the body. The elimination of OTC in muscle was slower compared with fish and other crustaceans. A dose of 40 mg kg⁻¹ is suggested for practical use.