Bioavailability and absorption analysis of oxytetracycline orally administered to the standardized moulting farmed Pacific white shrimps (Penaeus vannamei)

Dosing information of the major antibiotics: Oxytetracycline (OTC) in the Pacific white shrimp (P. vannamei) is necessary for aquaculture in Thailand. The aim of this study was to assess the oral bioavailability as well as to have more detailed pharmacokinetics of OTC in farmed P. vannamei with standardized moulting stage. 39 adult male P. vannamei with inter-moulting stage of C–D0 were employed. Individual animals were accurately dosed at 50 μg/g-body weight by forced feeding with a diet containing OTC 20 mg/g. Shrimps were sampled in 3 replicates at time intervals of 0.25, 0.5, 2, 4, 6, 9, 12, 24, 48, 72, 170, 336 and 504 h post-dose. The OTC levels with time intervals in biological matrices including hemolymph and hepatopancreas of each sample were determined by a validated HPLC method. The oral bioavailability was found to be 80.62% with low variability (SD 2.54%) due to the standardized animals utilized. It was evident that OTC orally and intra-sinusly administered may share pharmacokinetics in common. The 3-compartment with hepatopancreas “first-pass” elimination model could be successfully fitted into OTC levels both in hemolymph and in hepatopancreas. The absorption analysis could approximate the gastric emptying half-life of OTC of 1.6–4.3 h that was comparable to gastric emptying of food in related species suggesting that the solid drug and food uptake may be handled in somewhat similar manner for introduction into the shrimp's body.