Abstract

Oxytetracycline (OTC) is used in Chilean salmonid farming for bacterial pathogens treatment, mainly orally administered. Oral bioavailability of OTC in salmonids is low, so a high percentage of the dose is excreted by fishes. To increase OTC oral absorption, Zn-alginate microparticles were developed by spray drying, with a yield of 59.09%. An in vivo study was performed using Oncorhynchus mykiss (Rainbow trout) to compare OTC Znalginate micro-particles oral absorption in plasma and muscle matrices. Seven sampling points for plasma and four for muscle were considered. OTC was quantified in both matrices by UPLC-MS/MS. Results indicated a statistically significant difference between plasma concentrations of the OTC microparticles with respect to the commercial OTC formulation, reflecting a higher absorption of the microencapsulated drug, reaching maximum concentration 4 h earlier than the commercial formulation. In addition, the microparticles showed a release of OTC that remained constant for 12 h. In muscle, OTC microparticles reached twice the maximum concentration than the commercial formulation at 8 h. In conclusion, OTC microparticles improve the oral absorption of the molecule, which could allow drug delivery optimization and dose reduction in bacterial pathogens treatment in salmon production, consequently, decrease contamination of the environment with OTC residues.