Withdrawal times of freshwater rainbow trout, Salmo gairdneri Richardson, after treatment with oxolinic acid, oxytetracycline and trimetoprim

Abstract

. Oxolinic acid (OA), oxytetracyline (OTC) and trimetoprim (TMP) were investigated in whole gutted rainbow trout, Salmo gairdneri Richardson, and in their skin, muscle and blood, at 6, 12 and 18°C. Concentrations of drugs were measured by high‐pressure liquid chromatography. It is recommended that withdrawal times for rainbow trout be based on whole gutted rainbow trout and not, as in earlier investigations, from residual concentrations in muscle. Any concentrations in rainbow trout feed were found to be stable during the pelleting process used and up to 81 days after pelleting. The absorption of the drugs in rainbow trout show different temperature dependencies. A quantitative comparison of our overall data from this work with individual results from earlier investigations was undertaken. Suggested withdrawal times for freshwater rainbow trout treated with these drugs are: for OTC, 90 days below 6°C, 70 days between 6 and 12°C and 60 days above 12°C; for TMP, 60 days below 8°C and 40 days above 8°C; for OA, 20 days at approximately 18°C.

Multiple dose pharmacokinetic study of oxolinic acid in cod, Gadus morhua L.

“…Therefore, fish held in higher water temperatures obtain higher C max values, as absorption of xenobiotics seem to be more efficient with increasing temperature. Jacobsen (1989) and Coyne et al (2005) performed the only laboratory studies where oxolinic acid was administered by multiple oral dosing at various temperatures. Jacobsen (1989) studied the influence of temperature on withdrawal times for rainbow trout in fresh water and found oxolinic acid to be either independent of water temperature or diminish slightly with decreasing water temperature.…”

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“…The OTC residues were reduced >98% by the acid treatment with HCl. It is known that OTC forms complexes with di-cation, such as Ca 2+ and Mg 2+ , in hard tissues of fish (Grondel et al, 1987;Jacobsen, 1989;Rogstad et al, 1991;Namdari et al, 1996;Malvisi et al, 1996;Maruyama and Uno, 1997). In our previous works, Ca-tetracycline chelates accumulated in shrimp shells and were shown to be considerably stable (Uno et al, 2006a).…”

On the validity of setting breakpoint minimum inhibition concentrations at one quarter of the plasma concentration achieved following oral administration of oxytetracycline

“…In this work, data on the plasma concentration achieved 24 h after the end of therapy (C 24 ) was collected. The work of Elema et al (1996), Uno et al (1992), Jacobsen (1989) and Bjørklund and Bylund (1990) suggest that a reasonable estimate for the T max for orally administered OTC would be at 24 h and therefore that it is reasonable to employ C 24 as a proxy measure of C max .…”

“…Jacobsen (1989) reported a mean (n = 3) blood concentration of 0.69 mg/l in rainbow trout fed OTC for 8 days at 50 mg/kg. Herman et al (1969) fed OTC at 75 mg/kg for 14 days to various populations of trout and detected mean (n = 5) concentrations of 0.75, 0.9, 0.28 and 0.68 mg/l in their plasma.…”