New 2(1H)-quinoxalinones and their hexahydro derivatives were prepared for investigating their antimicrobial and antiinflammatory activities. The study showed that thiosemicarbazide 6a derived from the hexahydro-2(1H)-quinoxalinone series has nearly the same antibacterial activity as the reference drug ciprofloxacin. Moreover, the 2(1H)-quinoxalinones bearing N-phenyltriazole (9a) or 4-chlorophenyl-2,3-dihydrothiazole (13b) moieties were the most active ones after 4 h with use of the rat hind paw edema method, whereas their antiinflammatory and ulcerogenic activities were comparable with the selective COX-2 inhibitor celecoxib.

The pharmacokinetics of cefquinome were studied in healthy and Pasteurella multocida-infected rabbits after a single intramuscular (IM) injection at 2 mg/kg of its sulfate salt. Twelve female New Zealand white rabbits (2.0-2.5 kg) were used; six of them served as controls, and the other six had been infected with P. multocida; the experiments were conducted 1-2 days after nasal inoculation of P. multocida when rabbits showed the signs of respiratory infection. Plasma concentrations of cefquinome were determined using high-performance liquid chromatography. The values of elimination half-life, area under the curve, area under the first moment curve, and mean residence time were significantly lower in infected rabbits (0.48 hr, 4.54 hr*μg/ml, 3.63 hr* hr*μg/ml and 0.8 hr, respectively) than healthy rabbits (0.72 hr, 9.11 hr*μg/ml, 9.85 hr* hr*μg/ml and 1.1 hr, respectively), whereas total body clearance was significantly higher in infected than healthy rabbits. Therefore, P. multocida infection caused significant changes in some of the pharmacokinetic parameters of cefquinome in rabbits. These pharmacokinetic changes may affect dose regimen when used in P. multocida-infected rabbits.

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This study was designed to determine ceftiofur sodium residues of different rabbit tissues after intramuscular injection at a dose of 2.2 mg/kg BW. A total of twenty-four healthy male New Zealand White rabbits were divided into two groups; the first group (n = 21) was injected with ceftiofur for five successive days, while the second group (n = 3) untreated (control). Liver, kidney, pectoral and thigh muscles, spleen, heart, blood and lung from each rabbit were collected at the 1st, 3rd, 5th, 7th, 9th, 15th and 21st day post ceftiofur sodium treatment. Tissues were extracted and ceftiofur residues were analyzed using high-performance liquid chromatography (HPLC). Ceftiofur remained within the detectable level till the 5th day in most of the investigated tissues (liver, kidney, lung, heart, pectoral and thigh muscles) and serum, but still detected till the 7th and 9th day post treatment in lung and kidney, respectively. It can be concluded that rabbit muscles and livers could be consumed safely at the 3rd day post treatment with that dose, while, rabbit kidneys could be consumed safely at the 1st day post treatment with that dose without any hazards on consumers because the residual level is below the recommended MRL.

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The present study was designed to evaluate marbofloxacin residues in different rabbit tissues after multiple intramuscular administrations. For that purpose, rabbits were divided into two groups; the first group (n=21) administered 2mg/kg marbofloxacin for five successive days, while the second group (n=3) were untreated and served as controls. th and 21 st day after the last dose post administration of the drug. Liver, kidneys, pectoral muscle and thigh muscles, spleen, heart, blood and lung from each rabbit were taken, extracted and marbofloxacin residues were analyzed using high-performance liquid chromatographic method with ultraviolet detection. Results indicated a widespread distribution of marbofloxacin in the most tested tissues. It remained within detectable level till the 5 th day in liver and serum while it continues till the 7 th in kidneys day following the last dose. Therefore, muscles of rabbits treated with marbofloxacin could be consumed safely following the 1 st day post treatment, while liver and kidneys could be consumed safely in the 3 rd day after treatment without any hazards on consumers as the residual level below the recommended MRL (150µg/kg).

The aim of the present study was to detect the tilmicosin residues in muscles, kidneys and liver of broiler chickens and to investigate its impact on both cardiac enzymes and some hematological parameters. Seventy broiler chickens were divided into two groups; the first was left as a negative control. The second group was given tilmicosin orally (30 mg/kg BW) once/day for three successive days. Reversed phase-high performance liquid chromatography (RP-HPLC) with UV detector at 287 nm and solid phase extraction were used for detecting drug residues in tissue samples. Results indicated a widespread distribution of tilmicosin in most tested tissues. All tissue samples were considered tilmicosin free at the 9 th day after the last oral dose except liver. Tilmicosin elicited a significant reduction in red blood cells count, hemoglobin concentration, packed cell volume, lymphocytes and eosinophiles. On the other hand, heterophiles count and the mean corpuscular volume were increased significantly. White blood cells, monocytes, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration showed non-significant changes. Levels of all cardiac enzymes (Aspartate aminotransferase, lactate dehydrogenase, creatine kinase-MB and Troponin I) were high.