Pharmacokinetics and Tissue Residue Profiles of Enrofloxacin in Nile Tilapia <scp> <i>Oreochromis niloticus</i> </scp> Following a Single Oral Administration

The increasing frequency of bacterial diseases in aquaculture has necessitated the use of several antibiotics, including enrofloxacin (ENF), a broad-spectrum fluoroquinolone. The pharmacokinetic (PK) and pharmacodynamic (PD) data on ENF under tropical aquaculture conditions remain scarce. This study investigated the PK profile, tissue accumulation, and depletion pattern of total active fluoroquinolone (ENF + CIP) in Nile tilapia Oreochromis niloticus following a single oral dose of 10 mg/kg biomass. The ENF demonstrated rapid absorption, with peak plasma concentration (C_max) of 1.33 ± 0.21 μg/mL at 0.59 h (T_max), and extensive tissue distribution, particularly in bile (C_max: 16.26 ± 0.50 μg/mL) and intestine (C_max: 7.08 ± 0.28 μg/g). Elimination half-lives (t_1/2β) varied among tissues, with prolonged persistence in skin (t_1/2β: 693.18 h) and gills (t_1/2β: 237.47 h), indicating slow depletion. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ENF indicated its high effectiveness against Aeromonas hydrophila (0.20 μg/mL), while Streptococcus agalactiae exhibited comparatively lower sensitivity (MIC: 1.56 μg/mL; MBC: 6.25 μg/mL). The PK/PD integration revealed that ENF achieved optimal therapeutic levels against A. hydrophila, but suboptimal levels for S. agalactiae under a single-dose regimen. These findings underscore the need for tailored dosing strategies and highlight the importance of pharmacokinetic and microbiological data for responsible antibiotic use in aquaculture.