Bath immersion pharmacokinetics of florfenicol in Nile tilapia (Oreochromis niloticus)

Abstract

Drug administration by immersion can be a preferable method in certain conditions especially for treating small‐sized, anorexic, or valuable fish. Pharmacokinetic information regarding bath treatment is considerably lacking in comparison to other common administration routes. The current study aimed to investigate if immersion can be an effective route to administer florfenicol (FF) for treatment in Nile tilapia. Nile tilapia reared at 28°C were immersed with FF solution at concentrations of 50, 100, 200, 500, and 500/200 (3 hr/117 hr) ppm for 120 hr and moved to drug‐free freshwater for another 24 hr. The serum FF concentration in 100, 200, and 500/200 ppm groups reached steady‐state at 12 hr with concentrations of 2.44, 3.04, and 5.26 µg/ml, respectively, which were about 2% of the bathing concentrations. The target therapeutic levels of 1–4 µg/ml were attained and maintained within 1–12 hr, depending on the immersion concentration and the target MIC. Serum FF reached the target with shorter time at higher bathing concentration. Following the 120‐hr bath, the serum FF declined with the first‐order half‐life of approximately 10 hr. A minimum of 100 ppm FF is required for treatment purpose, and an initial high loading concentration followed by maintenance concentration is a plausible way to reach in vivo therapeutic level in short time. Greater than 99% of the residual FF in the bathing water could be removed within 15 min by 0.05% NaOCl. Our results indicated that bath immersion is a promising potential route for FF administration in Nile tilapia.

Temperature‐dependent pharmacokinetics of trichlorfon in common carp (Cyprinus carpio L.) after bath immersion therapy

“…In this study, C max of TCF in the plasma was low (70.76 µg/L), which is ~0.2% of the bathing concentration, compared with that of other previously tested compounds. The exact dose taken up by individual fish (in mg/kg body weight) was unknown, and the absolute bioavailability after bath immersion therapy cannot be pharmacokinetically calculated (Rairat et al, 2020). Nevertheless, the extent of drug uptake via this route can be evaluated by comparing the plasma concentration with the bath water concentration.…”

Differential effects of aquatic anaesthetics on the pharmacokinetics of antibiotics: Examples using florfenicol in Nile tilapia (Oreochromis niloticus)

“…The potential drug–drug interactions between the anaesthetic agent and the investigated drug during the drugs’ absorption, distribution, metabolism and elimination phases may further complicate the situation. Hence, it is advisable that the use of anaesthetics in pharmacokinetic studies should be avoided whenever possible (Horsberg, 1994; Kleinow et al., 1992), as was the case in our earlier studies with florfenicol (FF) in Nile tilapia ( Oreochromis niloticus ) (Rairat et al., 2019, 2020; Rairat, Thongpiam, et al., 2020). Unfortunately, unless the anaesthetic agent is used, drug administrations either via injection or oral gavage, as well as blood collections from the needle, are often infeasible for many fish species such as koi carp ( Cyprinus carpio ), largemouth bass ( Micropterus salmoides ), Asian seabass ( Lates calcarifer ) and rainbow trout ( Oncorhynchus mykiss ) due to their hyperactivities (based on our experience).…”

Pharmacokinetics, withdrawal period and risk assessment of enrofloxacin in the northern snakehead (Channa argus) following bath administration

“…Injection and oral gavage can guarantee accurate dosing, but they are impractical due to high labor costs and stress on the fish (Kent, 2015; Zhang, Cui et al., 2021; Zhang, Wang et al., 2021). Medicated feed was often preferred in situation where most of the fish are able to eat, but actual dose intake could not be ascertained (Kent, 2015; Rairat et al., 2020; Terzi et al., 2020). Bath treatment is a practical way, when the sick fish become anorexic (O"Grady et al., 1988).…”