Chicken, tissue residue depletion studies

The pharmacokinetic characteristics of florfenicol have been described in goats (40), calves (41), and chickens (42). The efficacy of florfenicol in aquaculture has been also demonstrated against bacteria involved in some major fish pathologies, especially in salmon and trout (43, 44). Pharmacokinetic studies in Atlantic salmon indicated that the compound was well absorbed and distributed following oral administration (45). Tissue residue depletion studies after an oral daily administration of 10 mg/kg bw florfenicol in rainbow ftout at 10 C for 10 days showed that muscle/skin tissue contained 150 ppb drug at 15 days after the last dose (46). 

Residue depletion studies in pigs fed 330 mg kitasamycin/kg feed for 14 days showed that at zero withdrawal only liver (100 ppb) and kidney (60 ppb) contained detectable residues. One day after withdrawal of the treatment, residual antibiotic activity was detectable only in the liver. Residue depletion studies in chickens fed 500 mg kitasamycin/kg feed for 14 days showed that at zero withdrawal only liver (70 ppb) contained detectable residues. One day after withdrawal, residual antibiotic activity could not be detected in any tissue. 

Residue depletion studies in cattle, swine, sheep, chickens, and turkeys given oral forms of oxytetracycline including feed premixes, soluble powders, and tablets showed that residues in all edible tissues, with the exception of kidney, were cleared of detectable amounts of oxytetracycline within 5 days postdose. Injectable forms of oxytetracycline yielded higher residue levels that persisted longer than the oral forms, while long-acting formulations of oxytetracycline required extended withdrawal periods (234). 

Other residue depletion studies of dimetridazole in chickens, turkeys, and swine generally showed that the concentrations of dimetridazole residues decreased to less than 0.1 ppm in the edible tissues of chickens at 1 day withdrawal, and to less than 2 ppm in the edible tissues of turkeys and swine at 2-day withdrawal (9, 10). 

Pharmacokinetic studies have shown that most salinomycin appears in feces in the form of an inactive metabolite that is subsequently degraded with a half-life of less than 50 h. Residue depletion studies in chickens showed wide variation in the concentrations of residues appearing in edible tissues. Some workers have reported levels of salinomycin residues as high as 1100 ppb in liver of chickens at 0 withdrawal (34, 35). In contrast, other workers reported residue levels as low as 3 ppb in the same tissue under similar experimental conditions (36). 

Toltrazuril residue depletion studies in chickens orally given 14.1 mg/kg bw/day for 2 consecutive days per week, three times at a week interval, showed that the concentrations of the parent drug were 342, 1845, 870, 1332, and 1077 ppb in muscle, fat, skin, liver, and kidney, respectively, 1 day after the cessation of treatment. These concentrations declined thereafter to reach, at 6 days after dosing, 10, 81, 33, 22, and 15 ppb in muscle, fat, skin, liver, and kidney, respectively. At 10 days postdosing, 24 ppb were found in fat and 11 ppb in skin, whereas other tissues did not contain detectable residue levels. 

The metabolic fate of nicarbazin was similar in chickens and rats with DNC and HDP being metabolised independently of one another. HDP underwent little metabolism and was rapidly cleared from tissues. DNC was metabolised by reduction and acetylation and was cleared less rapidly. Residue depletion studies in chickens showed that normal use of nicarbazin would not result in toxicologically significant levels of HDP in tissues and that consumer safety would be dictated by the concentrations of DNC. Co-administration of nicarbazin and narasin to chickens increased concentrations of residues of DNC by 20% in liver to 50% in muscle. ... 

For enrofloxacin, there is an additional consideration in relation to pharmacokinetic and residue profiles, in that it is metabolized in the liver to a micro-biologically active metabolite, ciprofloxacin, by a deethylation reaction. In cattle and calf conversion rates, from enrofloxacin to ciprofloxacin, are 25% and 41%, respectively. Residues are measured as the sum of enrofloxacin and ciprofloxacin. In poultry, pigs, and flsh, much smaller amounts of ciprofloxacin are formed. Nevertheless, in chickens, ciprofloxacin residues were detectable 12 days after dosing with enrofloxacin. Ciprofloxacin itself is converted to minor metabolites with no antibacterial activity. Nevertheless, metabolites are of residue concern, and tissue depletion profiles were studied in broiler chickens by Anaddn et al. The data in Table 2.6 illustrate the rapid conversion of ciprofloxacin to oxociprofloxacin and desethyleneciprofloxacin (Tmax <1-0 h), the accumulation... 

Radiotracer Studies in Poultry. The radiotracer study characterized the depletion of total residues in edible tissues of 37-day old broiler chickens that received 7-day s ad libitum access to feed medicated with 25 ppm l4C-semduramicin sodium. Residues in edible tissues were determined at 6,12,24,48 and 120 hours after treatment. The tissue containing the highest total residues at all withdrawal times was liver. Liver residues were 1.8 or more times higher than residues in the next highest tissues, fat or skin. Total residues in liver were depleted from a mean value of 0.273 pg/g at 6 hours to 0.058 pg/g at 24 hours, and eventually to 0.018 pg/g at 120 hours (Table II). 

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