Long Depletion Time of Enrofloxacin in Rainbow Trout ( Oncorhynchus mykiss )

Abstract

The international production of farmed fish has been growing continuously over recent years. Until now few veterinary drugs have been approved by the European Union for use in aquaculture, and this has favored the off-label use of products authorized for use in food-producing animal species different from fishes among fish farmers. Adequate field studies are lacking, especially for those species called minor species which are consumed extensively only in some European countries. In the present investigation we studied the depletion of the fluoroquinolone antibacterial enrofloxacin over time in a minor species, the rainbow trout (Oncorhynchus mykiss), reared on a real fish farm and treated with medicated feed (10 mg kg of trout body weight ؊1 day ؊1 ). Edible tissue samples (muscle plus skin in natural proportions) and fish bone samples were analyzed for enrofloxacin and for its major metabolite, ciprofloxacin, by high-performance liquid chromatography with fluorescence detection at different times after the end of treatment. Our results show that at 500°C-day (in which degree-days are calculated by multiplying the mean daily water temperature by the total number of days on which the temperature was measured), which is the minimum withdrawal period established by European Economic Commission Directive No. 82/2001 for any type of product administered off-label, edible trout tissues might still contain about 170 g of enrofloxacin kg ؊1 , whereas the maximum residue level for enrofloxacin plus ciprofloxacin is set at 100 g kg ؊1 . To our knowledge, no studies of the depletion of enrofloxacin in rainbow trout have been performed. On the basis of the data obtained in the present study, we suggest a more appropriate withdrawal time of 816°C-day for the sum of enrofloxacin plus ciprofloxacin levels in rainbow trout muscle plus skin tissues.

Residues of fluoroquinolones in marine aquaculture environment of the Pearl River Delta, South China

“…Generally, FQs may be absorbed and formed as a metabolite, which has a long depletion time in fish tissues (Lucchetti et al 2004). The average biological half-life of FQs is 3-10 h due to the accumulation of FQs in serum (Hopper and Wolfson 1985).…”

Elimination of enrofloxacin in striped catfish (Pangasianodon hypophthalmus) following on-farm treatment

“…Based on a pond water temperature of 30°C, a withdrawal time for ENR and CIP of 45 days are required to meet the MRL of the EU, while a 62 days withdrawal period is needed for rainbow trout (Oncorhynchus mykiss) treated with ENR at dose of 10 mg/kg of body weight per day for five consecutive days in field conditions (12-13°C) (Luccheti et al, 2004). The fact that the suggested withdraw time of 45 days for striped catfish treated with ENR is lower than for treated rainbow trout (62 days) seems to be due to the higher temperature (29-31°C, Table), as for other aquatic species, the elimination rates of drugs appears to be accelerated with rising water temperatures (Luccheti et al, 2004;Xu et al, 2006). It should be noted that our suggested withdraw time of 45 days for striped catfish treated with ENR to meet the EU MRL is longer than the 30 days withdraw time suggested by producers of ENR.…”

Effect of Storage on Residue Levels of Enrofloxacin in Muscle of Rainbow Trout (Oncorhynchus mykiss) and Common Carp (Cyprinus carpio)

“…Enrofloxacin is among the few drugs licensed for use in aquatic species with established Maximum Residual Limits of 100 μg/kg as the sum of the levels of enrofloxacin and ciprofloxacin in tissues (11). Literature data indicates variable withdrawal time in different fish species (12). Therefore depletion of drugs from edible tissues must be assessed in order to offer safe food on the market.…”