Oxytetracycline (OTC) is a broad-spectrum antibiotic that acts by inhibiting protein synthesis in bacteria. Oxytetracycline prevents the binding from aminoacil-tRNA to the complex m-ribosomal RNA. Oxytetracycline also possesses anti-HSV-1 activity[1][2][3].

Oxytetracycline is an important member of the bacterial aromatic polyketide family, which is a structurally diverse class of natural products. Oxytetracycline is synthesized by a type II polyketide synthase that generates the poly-beta-ketone backbone through successive decarboxylative condensation of malonyl-CoA extender units, followed by modifications by cyclases, oxygenases, transferases, and additional tailoring enzymes[2].

For Oxytetracycline, the limits are 100 μg/kg in muscle and milk, 200 μg/kg in egg, 300 μg/kg in liver and 600 μg/kg in kidney. Oxytetracycline (OTC) is administered to fish as medicated feed at concentrations ranging from 35 to 75 mg a.i kg-1 biomass day-1 for 7-14 days[1]. The effects of administration a therapeutic dose of Oxytetracycline (82.8 mg/kg of bw to 1 % bw/day) for 10 days are species specific. Oxytetracycline increases the relative liver weight in Morone chrysops x M. saxatilis, the enzymatic activity of CYP3A4 in Ictalurus punctatus, protein expression of CYP3A4 in Oreochromis niloticus and depleted the hepatic CYP3A4 in the latter[1].