Valutazione della biodisponibilità di ossitetraciclina microincapsulata a seguito di somministrazione orale singola e protratta nella trota (Salmo trutta trutta) e nel branzino (Dicentrarchus labrax).

To improve the oral absorption of oxytetracycline (OTC) in fish, some researches was already undertaken including the drug in several matrices (saturated and unsaturated fatty acids, starch, pectine and alginate) without satisfying results. The aim of this research was to assess a new formulation encapsulated in etheroglycosides (OTC test) in brown trout (Salmo trutta trutta) and seabass (Dicentrarchus labrax) after single and repeated administrations, compared with the commercial formulation (OTC reference). Two hundred and sixty brown trout and seabass were used both in single and repeated administration. Medicated feed containing 4.5 g/kg of OTC test or 7.5 g/kg of OTC reference product were given to fish at the rate of 1% biomass. Blood samples were collected at scheduled times and serum was stored at -20° C until analysis performed by HPLC after solid-phase extraction. In brown trout after single administration the value of AUC of the reference formulation was lower than the corresponding one of the test product: 11.84 vs 13.40 (μg/ml)h; the opposite occurred after repeated administrations: 75.28 and 79.50 (μg/ml)h respectively for OTC test and OTC reference. In seabass the reference oxytetracycline showed the greatest AUCs values both after single and repeated administration: 34.11 and 57.53 (μg/ml)h vs 25.95 and 41.59 (μg/ml)h. The relative bioavailabilities, rectified by the concentrations in the diet were 187 and 156 % in brown trout and 126 and 122 % in seabass, attesting for a better absorption of the test product.