ceftiofur and desfuroylceftiofur

The objective of this study was to compare the plasma pharmacokinetic profile of ceftiofur crystalline-free acid (CCFA) and ceftiofur sodium in neonatal calves between 4 and 6 days of age. In one group (n = 7), a single dose of CCFA was administered subcutaneously (SQ) at the base of the ear at a dose of 6.6 mg/kg of body weight. In a second group (n = 7), a single dose of ceftiofur sodium was administered SQ in the neck at a dose of 2.2 mg/kg of body weight. Concentrations of desfuroylceftiofur acetamide (DCA) in plasma were determined by HPLC. Median time to maximum DCA concentration was 12 h (range 12-48 h) for CCFA and 1 h (range 1-2 h) for ceftiofur sodium. Median maximum plasma DCA concentration was significantly higher for calves given ceftiofur sodium (5.62 μg/mL; range 4.10-6.91 μg/mL) than for calves given CCFA (3.23 μg/mL; range 2.15-4.13 μg/mL). AUC0-∞ and Vd/F were significantly greater for calves given CCFA than for calves given ceftiofur sodium. The median terminal half-life of DCA in plasma was significantly longer for calves given CCFA (60.6 h; range 43.5-83.4 h) than for calves given ceftiofur sodium (18.1 h; range 16.7-39.7 h). Cl/F was not significantly different between groups. The duration of time median plasma DCA concentrations remained above 2.0 μg/mL was significantly longer in calves that received CCFA (84.6 h; range 48-103 h) as compared to calves that received ceftiofur sodium (21.7 h; range 12.6-33.6 h). Based on the results of this study, CCFA administered SQ at a dose of 6.6 mg/kg in neonatal calves provided plasma concentrations above the therapeutic target of 2 μg/mL for at least 3 days following a single dose. It is important to note that the use of ceftiofur-containing products is restricted by the FDA and the use of CCFA in veal calves is strictly prohibited.

Topics: Animals; Animals, Newborn; Anti-Bacterial Agents; Area Under Curve; Cattle; Cephalosporins; Half-Life

Administration of ceftiofur sodium via nebulisation has been recommended for the treatment of bronchopneumonia in horses, despite the lack of pharmacokinetic and safety data.. To compare concentrations of desfuroylceftiofur acetamide (DCA) in plasma and pulmonary epithelial lining fluid (PELF) of foals after nebulisation or i.m. administration of ceftiofur sodium and to determine if nebulisation of ceftiofur sodium induces airway inflammation.. Randomised experimental study.. Six weanling foals received ceftiofur sodium (2.2 mg/kg bwt daily for 5 doses) by the i.m. route and 6 foals received the same dose by nebulisation. Concentrations of DCA in plasma and PELF were measured after Doses 1 and 5, and differential cell counts were performed on bronchoalveolar lavage samples obtained after Dose 5.. Foals receiving ceftiofur sodium via nebulisation had significantly lower peak concentrations (0.15 ± 0.12 vs. 6.15 ± 0.75 mg/l) and area under the curve (1.26 ± 0.96 vs. 37.63 ± 4.01 mg●h/l) in plasma compared with those receiving the drug by the i.m. route. In contrast, foals receiving ceftiofur sodium via nebulisation had significantly higher peak concentrations (4.52 ± 2.91 vs. 0.73 ± 0.73 mg/l) and area under the curve (24.14 ± 14.09 vs. 5.91 ± 3.28 mg●h/l) in PELF compared with those receiving the drug by the i.m. route. Cell concentration and differential cell count in bronchoalveolar lavage fluid of foals nebulised with ceftiofur sodium were not significantly different from those of foals nebulised with saline.. Administration of ceftiofur sodium via nebulisation is well tolerated and DCA concentrations in PELF remain above the minimum inhibitory concentration of the drug required to inhibit the growth of 90% of Streptococcus zooepidemicus for approximately 24 h after administration. Nebulised ceftiofur sodium warrants further investigation for the treatment of bacterial infections of the lower respiratory tract in horses.

Topics: Administration, Inhalation; Aerosols; Animals; Body Fluids; Bronchoalveolar Lavage Fluid; Cephalosporins; Horses; Injections, Intramuscular; Lung

Current labelling for the use of ceftiofur crystalline free acid (CCFA) in horses states that 2 i.m. doses must be administered 4 days apart to provide 10 days of therapeutic coverage. A 10 day treatment regimen is not sufficient for the long-term treatment of horses with severe lung consolidation or pleuropneumonia. There are currently no data to guide an appropriate dosing interval when a longer treatment regimen is warranted.. To determine steady-state plasma and pulmonary epithelial lining fluid (PELF) concentrations of desfuroylceftiofur acetamide (DCA) after weekly i.m. administration of CCFA to adult horses.. Experimental study.. Seven adult horses received i.m. CCFA at a dose of 6.6 mg/kg bwt on Day 0, Day 4 and every 7 days thereafter for 3 additional doses. Concentrations of DCA in plasma and PELF were measured at various time intervals.. After weekly i.m. administration, the mean (± s.d.) steady-state peak DCA concentration in plasma (2.87 ± 1.50 μg/ml) was significantly higher than that in PELF (0.84 ± 0.53 μg/ml). Mean terminal half-lives in plasma (77.5 ± 17.5 h) and PELF (92.8 ± 59.0 h) were not significantly different. Concentrations of DCA in plasma and PELF remained in the therapeutic range for the entire dosing interval.. After the initial 2-dose regimen 4 days apart, weekly i.m. administration of CCFA was well tolerated and resulted in plasma and PELF DCA concentrations above the minimal inhibitory concentration that inhibits growth of at least 90% of common lower respiratory tract pathogens of horses.. Weekly administration of CCFA would appear appropriate when a treatment regimen longer than 10 days is warranted based on clinical signs and disease severity.

Topics: Animals; Anti-Bacterial Agents; Area Under Curve; Cephalosporins; Drug Administration Schedule; Female; Half-Life; Horses; Lung

Cefotaximase-Munich (CTX-M) extended-spectrum beta-lactamases (ESBLs) are commonly associated with Gram-negative, hospital-acquired infections worldwide. Several beta-lactamase inhibitors, such as clavulanate, are used to inhibit the activity of these enzymes. To understand the mechanism of CTX-M-15 activity, we have determined the crystal structures of CTX-M-15 in complex with two specific classes of beta-lactam compounds, desfuroylceftiofur (DFC) and ampicillin, and an inhibitor, clavulanic acid. The crystal structures revealed that Ser70 and five other residues (Lys73, Tyr105, Glu166, Ser130, and Ser237) participate in catalysis and binding of those compounds. Based on analysis of steady-state kinetics, thermodynamic data, and molecular docking to both wild-type and S70A mutant structures, we determined that CTX-M-15 has a similar affinity for all beta-lactam compounds (ceftiofur, nitrocefin, DFC, and ampicillin), but with lower affinity for clavulanic acid. A catalytic mechanism for tested β-lactams and two-step inhibition mechanism of clavulanic acid were proposed. CTX-M-15 showed a higher activity toward DFC and nitrocefin, but significantly lower activity toward ampicillin and ceftiofur. The interaction between CTX-M-15 and both ampicillin and ceftiofur displayed a higher entropic but lower enthalpic effect, compared with DFC and nitrocefin. DFC, a metabolite of ceftiofur, displayed lower entropy and higher enthalpy than ceftiofur. This finding suggests that compounds containing amine moiety (e.g., ampicillin) and the furfural moiety (e.g., ceftiofur) could hinder the hydrolytic activity of CTX-M-15.

Topics: Ampicillin; Anti-Bacterial Agents; beta-Lactamases; Cephalosporins; Clavulanic Acid; Microbial Sensitivity Tests; Molecular Docking Simulation

Eight clinically normal and drug-naïve Holstein steers were dosed with ceftiofur sodium at 2.2 mg/kg body weight intramuscularly. Doses were given at 24-h intervals for 5 days. Prior to the first dose and after all injections, blood samples were collected serially for determination of plasma concentrations of one of ceftiofur's main metabolites, desfuroylceftiofur cysteine disulfide (DCCD). A nonlinear mixed-effect model was used to analyze the plasma concentration data. A stochastic approximation expectation maximization (SAEM) algorithm in MONOLIX version 4.2.2 was used to approximate the likelihood of the nonlinear mixed-effect model and to estimate the population parameters. In addition, simulation studies were conducted to justify the model and demonstrate how to interpret the model parameters given different scenarios.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cephalosporins; Computer Simulation; Male; Models, Biological; Software

Healthy farm animals have been found to act as a reservoir of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli). Therefore, the objective of the study was to determine the input of antimicrobial active ceftiofur metabolites in the stable via faeces and urine after intramuscular administration of the drug to pigs and the elucidation of the Escherichia coli ESBL resistance pattern of treated and untreated pigs housed in the same barn during therapy.. For determination of the minimal inhibitory concentration (MIC) the method of microdilutionaccording to the recommended procedure of the Clinical and Laboratory Standards Institute was used. Inaddition to that, a qualitative determination was performed by agar dilution. Unsusceptible E. coli speciesselected via agar dilution with cefotaxime were confirmed by MALDI-TOF and ESBL encoding genes wereidentified by PCR. The amounts of ceftiofur measured as desfuroylceftiofur (DFC) in the different probes (plasma, urine, faeces and dust) were analysed by UPLC-MS/MS.. In a first experiment two groups of pigs (6 animals per group) were housed in the same barn in two separated boxes. One group (group B) were treated with ceftiofur according to the licence (3 mg/kg administered intramuscularly (i.m.) on three consecutive days, day 1-3). During a second treatment period (day 29-31) an increased rate of ESBL resistant E. coli was detectable in these treated pigs and in the air of the stable. Moreover, the second group of animals (group A) formerly untreated but housed for the whole period in the same stable as the treated animals revealed increased resistance rates during their first treatment (day 45-47) with ceftiofur. In order to investigate the environmental input of ceftiofur during therapy and to simulate oral uptake of ceftiofur residues from the air of the stable a second set of experiments were performed. Pigs (6 animals) were treated with an interval of 2 weeks for 3 days with different doses of ceftiofur (3 mg/kg, 1 mg/kg and 0.3 mg/kg i.m.) as well as with 3 mg/kg per os) and the renal and biliary excretion of ceftiofur as its active metabolite were measured in comparison to the plasma levels. In addition to that, probes of the sedimentation dust and the air of the stable were analysed for drug residues.. The present study shows that treatment of several animals in a stable with ceftiofur influences the resistance pattern of intestinal Escherichia coli of the treated as well as untreated animals housed in the same stable. During therapy with the drug which was administered by injection according to the licence we detected nameable amounts of ceftiofur and its active metabolites in the dust and air of the stable.

Topics: Animals; Anti-Bacterial Agents; Cephalosporins; Disease Susceptibility; Drug Resistance, Bacterial; Escherichia coli Infections; Feces; Female; Housing, Animal; Injections, Intramuscular; Microbial Sensitivity Tests; Swine; Swine Diseases

To compare pharmacokinetics after a single IM or SC injection of ceftiofur crystalline-free acid (CCFA) to bearded dragons (Pogona vitticeps).. 8 adult male bearded dragons.. In a preliminary experiment, doses of 15 and 30 mg/kg, SC, were compared in 2 animals, and 30 mg/kg resulted in a more desirable pharmacokinetic profile. Then, in a randomized, complete crossover experimental design, each bearded dragon (n = 6) received a single dose of 30 mg of CCFA/kg IM or SC; the experiment was repeated after a 28-day washout period with the other route of administration. Blood samples were collected at 10 time points for 288 hours after injection. Plasma concentrations of ceftiofur and desfuroylceftiofur metabolites were measured via reverse-phase high-performance liquid chromatography. Data were analyzed with a noncompartmental model.. No adverse effects were observed. Plasma concentrations greater than a target minimum inhibitory concentration of 1 μg/mL were achieved by 4 hours after administration by both routes. Mean plasma concentrations remained > 1 μg/mL for > 288 hours for both routes of administration.. A single dose of CCFA (30 mg/kg) administered IM or SC to bearded dragons yielded plasma concentrations of ceftiofur and its metabolites > 1 μg/mL for > 288 hours. The SC route would be preferred because of less variability in plasma concentrations and greater ease of administration than the IM route. Future studies should include efficacy data as well as evaluation of the administration of multiple doses.

Topics: Animals; Anti-Bacterial Agents; Cephalosporins; Chromatography, High Pressure Liquid; Cross-Over Studies; Dose-Response Relationship, Drug; Half-Life; Injections, Intramuscular; Injections, Subcutaneous; Lizards; Male; Microbial Sensitivity Tests; Random Allocation; Time Factors

Ceftiofur is a widely used cephalosporin β-lactam antibiotic with frequently reported residue violations. This paper reports a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determining a ceftiofur metabolite, desfuroylceftiofur cysteine disulfide (DCCD), in bovine kidney, liver, and muscle tissues. Incurred tissue samples were obtained from dosed animals and analyzed to evaluate the utility of the method. For kidney, the target tissue, the method utilized a simple extraction with phosphate buffer followed by solid phase extraction (SPE) cleanup. For liver and muscle, acetonitrile and hexane were used to remove most proteins and fat from the initial buffer extract before the SPE cleanup. Method accuracy was between 97 and 107%, and the coefficient of variation was between 3.4 and 11.0% for all three types of tissues. The relationship between the new and regulatory methods for bovine kidney was established. It was concluded that DCCD is a suitable surrogate marker residue for ceftiofur in bovine kidney.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cephalosporins; Chromatography, Liquid; Cysteine; Disulfides; Drug Residues; Kidney; Liver; Muscles; Tandem Mass Spectrometry

The objective of this study was to determine the pharmacokinetics of CCFA in mares with placentitis and evaluate the disposition of the drug in fetal fluids, fetal membranes, colostrum, and serum of foals. A secondary objective was to obtain pilot data regarding the efficacy of CCFA for improving foal survival in mares with placentitis. Twelve pregnant pony mares were enrolled in the study, inoculated with Streptococcus zooepidemicus, intracervically and assigned to one of three groups: CEFT (n = 3; administered CCFA only; 6.6 mg/kg, i.m., q96h); COMBO (n = 6; administered combination therapy of CCFA, altrenogest, and pentoxifylline); UNTREAT (n = 3, no treatment). Treatment was initiated at the onset of clinical signs. Concentrations of desfuroylceftiofur acetamide (DCA), the acetamide derivative of ceftiofur and desfuroylceftiofur metabolites, were measured using high-performance liquid chromatography. Maximum and minimum serum concentrations of DCA at steady state in treated mares were 2.40±0.40 μg/mL and 1.06±0.29 μg/mL, respectively. Concentration of DCA in colostrum was 1.51±0.60 μg/mL. DCA concentrations in placenta and fetal tissues were very low (median = 0.03 μg/mL) and below the minimum inhibitory concentration of relevant pathogens. DCA was not detected in amniotic fluid or foal serum. Treatment did not appear to improve foal survival (CEFT: 0/3; COMBO: 2/6; UNTREAT: 2/3). Bacteria were recovered from the uterus of most mares postpartum and from blood cultures of most foals regardless of treatment.

Topics: Animals; Anti-Bacterial Agents; Cephalosporins; Colostrum; Extraembryonic Membranes; Female; Fetus; Horses; Placenta; Placenta Diseases; Pregnancy

Topics: Animals; Anti-Bacterial Agents; Cephalosporins; Female; Half-Life; Horses; Injections, Intramuscular; Injections, Subcutaneous; Statistics as Topic

The objectives of this study were to determine the plasma and pulmonary disposition of ceftiofur crystalline free acid (CCFA) in weanling foals and to compare the plasma pharmacokinetic profile of weanling foals to that of adult horses. A single dose of CCFA was administered intramuscularly to six weanling foals and six adult horses at a dose of 6.6 mg/kg of body weight. Concentrations of desfuroylceftiofur acetamide (DCA) were determined in the plasma of all animals, and in pulmonary epithelial lining fluid (PELF) and bronchoalveolar lavage (BAL) cells of foals. After intramuscular (IM) administration to foals, median time to maximum plasma and PELF concentrations was 24 h (12-48 h). Mean (± SD) peak DCA concentration in plasma (1.44 ± 0.46 μg/mL) was significantly higher than that in PELF (0.46 ± 0.03 μg/mL) and BAL cells (0.024 ± 0.011 μg/mL). Time above the therapeutic target of 0.2 μg/mL was significantly longer in plasma (185 ± 20 h) than in PELF (107 ± 31 h). The concentration of DCA in BAL cells did not reach the therapeutic level. Adult horses had significantly lower peak plasma concentrations and area under the curve compared to foals. Based on the results of this study, CCFA administered IM at 6.6 mg/kg in weanling foals provided plasma and PELF concentrations above the therapeutic target of 0.2 μg/mL for at least 4 days and would be expected to be an effective treatment for pneumonia caused by Streptococcus equi subsp. zooepidemicus at doses similar to the adult label.

Topics: Animals; Anti-Bacterial Agents; Bronchoalveolar Lavage Fluid; Cephalosporins; Female; Horses; Injections, Intramuscular; Lung; Male; Weaning

To determine the pharmacokinetic properties of 1 IM injection of ceftiofur crystalline-free acid (CCFA) in American black ducks (Anas rubripes).. 20 adult American black ducks (6 in a preliminary experiment and 14 in a primary experiment).. Dose and route of administration of CCFA for the primary experiment were determined in a preliminary experiment. In the primary experiment, CCFA (10 mg/kg, IM) was administered to ducks. Ducks were allocated into 2 groups, and blood samples were obtained 0.25, 0.5, 1, 2, 4, 8, 12, 48, 96, 144, 192, and 240 hours or 0.25, 0.5, 1, 2, 4, 8, 24, 72, 120, 168, and 216 hours after administration of CCFA. Plasma concentrations of ceftiofur free acid equivalents (CFAEs) were determined by use of high-performance liquid chromatography. Data were evaluated by use of a naive pooled-data approach.. The area under the plasma concentration versus time curve from 0 hours to infinity was 783 h•μg/mL, maximum plasma concentration observed was 13.1 μg/mL, time to maximum plasma concentration observed was 24 hours, terminal phase half-life was 32.0 hours, time that concentrations of CFAEs were higher than the minimum inhibitory concentration (1.0 μg/mL) for many pathogens of birds was 123 hours, and time that concentrations of CFAEs were higher than the target plasma concentration (4.0 μg/mL) was 73.3 hours.. On the basis of the time that CFAE concentrations were higher than the target plasma concentration, a dosing interval of 3 days can be recommended for future multidose CCFA studies.

Topics: Animals; Anti-Bacterial Agents; Area Under Curve; Cephalosporins; Chromatography, High Pressure Liquid; Ducks; Female; Half-Life; Injections, Intramuscular; Male

Ceftiofur is a cephalosporin β-lactam antibiotic widely used for treating certain bacterial infections in beef and dairy cattle. The regulatory HPLC-UV method for ceftiofur residues in animal tissues is time consuming and non-specific. Additionally, because the regulatory method involves chemical reactions to convert the metabolites into a single moiety, it is virtually impossible to incorporate the procedure into a multi-residue method. Ceftiofur residue violations in beef and dairy cattle have been frequently reported and therefore an improved method is needed. Herein we report a rapid and sensitive LC-MS/MS method for the determination and confirmation of ceftiofur metabolite, desfuroylceftiofur cysteine disulfide (DCCD), in bovine kidney tissue. The new method utilizes a simple extraction with phosphate buffer followed by SPE cleanup. A deuterated internal standard was synthesized and used for quantitation. The matrix-based calibration curve was linear from 25 to 2000 ng/g. The average accuracy for control kidney samples from six different sources fortified at 50-1000 ng/g was 97.7-100.2% with CV ≤ 10.1%. The limit of confirmation was 50 ng/g.

Topics: Animals; Cattle; Cephalosporins; Chromatography, Liquid; Cysteine; Drug Residues; Kidney; Least-Squares Analysis; Reproducibility of Results; Sensitivity and Specificity; Solid Phase Extraction; Tandem Mass Spectrometry

To determine the pharmacokinetics of a long-acting formulation of ceftiofur, ceftiofur crystalline-free acid (CCFA), following SC injection to Asian elephants (Elephas maximus).. 11 adult Asian elephants.. Each elephant received CCFA (6.6 mg/kg, SC) in the area caudoventral to the base of an ear. Blood samples were collected from an ear vein immediately prior to and at 0.5, 1, 2, 4, 8, 12, 24, 36, 48, 72, 96, 120, 144, and 168 hours after CCFA administration. Plasma concentrations of desfuroylceftiofur acetamide (the acetamide derivative of ceftiofur) were measured via ultrahigh-pressure liquid chromatography-tandem mass spectrometry. Data were analyzed via a noncompartmental pharmacokinetics approach.. The mean ± SD maximum plasma concentration of desfuroylceftiofur acetamide was 1.36 ± 0.74 μg/mL and was detected at 4718 ± 31.30 hours. The mean ± SD area under the curve from time 0 to infinity was 2278 ± 55.8 μg•h/mL, and the mean residence time from time 0 to infinity was 158.2 ± 90.2 hours. The terminal elimination half-life associated with the slope of the terminal phase had a harmonic mean ± pseudo-SD of 83.36 ± 30.01 hours.. Elephants tolerated CCFA at a dose of 6.6 mg/kg, SC, well. Dosing recommendations will depend on the mean inhibitory concentration of ceftiofur for each bacterial pathogen. Desfuroylceftiofur acetamide concentrations remained > 0.25 μg/mL for the entire 168-hour study period, which suggested CCFA would provide clinically relevant antimicrobial activity against certain pathogens for 7 to 10 days.

Topics: Animals; Anti-Bacterial Agents; Area Under Curve; Cephalosporins; Chromatography, High Pressure Liquid; Elephants; Female; Half-Life; Injections, Subcutaneous; Male

To evaluate the elimination pharmacokinetics of a single i.m. injection of a long-acting ceftiofur preparation (ceftiofur crystalline-free acid [CCFA]) in healthy adult helmeted guineafowl (Numida meleagris).. 14 healthy adult guineafowl.. 1 dose of CCFA (10 mg/kg) was administered i.m. to each of the guineafowl. Blood samples were collected intermittently via jugular venipuncture over a 144-hour period. Concentrations of ceftiofur and all desfuroylceftiofur metabolites were measured in plasma via high-performance liquid chromatography.. No adverse effects of drug administration or blood collection were observed in any bird. The minimal inhibitory concentration (MIC) for many bacterial pathogens of poultry and domestic ducks (1 μg/mL) was achieved by 1 hour after administration in most birds and by 2 hours in all birds. A maximum plasma concentration of 5.26 μg/mL was reached 19.3 hours after administration. Plasma concentrations remained higher than the MIC for at least 56 hours in all birds and for at least 72 hours in all but 2 birds. The harmonic mean ± pseudo-SD terminal half-life of ceftiofur was 29.0 ± 4.93 hours. The mean area under the curve was 306 ± 69.3 μg•h/mL, with a mean residence time of 52.0 ± 8.43 hours.. A dosage of 10 mg of CCFA/kg, i.m., every 72 hours in helmeted guineafowl should provide a sufficient plasma drug concentration to inhibit growth of bacteria with an MIC ≤ 1 μg/mL. Clinical use should ideally be based on bacterial culture and antimicrobial susceptibility data and awareness that use of CCFA in avian patients constitutes extralabel use of this product.

Topics: Animals; Anti-Bacterial Agents; Area Under Curve; Cephalosporins; Chromatography, High Pressure Liquid; Female; Galliformes; Half-Life; Injections, Intramuscular; Male

Ceftiofur sodium is a third generation broad-spectrum cephalosporin, formulated as an intramuscular injection, which is used to treat respiratory diseases in swine, ruminants and horses. The thioester bond on ceftiofur is rapidly cleaved to give desfuroylceftiofur which is further metabolized to a disulfide dimer and various desfuroylceftiofur-protein and amino acid conjugates. Methods of analysis of ceftiofur rely on cleavage by dithioerythritol to produce desfuroylceftiofur, which is further stabilized by derivatization to desfuroylceftiofur acetamide using iodoacetamide. Previous analytical methods have extracted derivatized analyte from plasma and tissue using solid-phase extraction clean-up steps followed by HPLC analysis with results reported as ceftiofur-free acid equivalents (CFAE). The simplified method presented here involves direct HPLC injection of a cleaved and derivatized sample following a protein precipitation step with calibration by external standardization and selectivity achieved based on chromatography and diode-array detection (DAD). The assay was linear over the calibration range 0.4-40 microg/ml in plasma. Intra-batch reproducibility R.S.D. was 10.3% and intra-batch sample repeatability R.S.D. was 2.1% at the 5 microg/ml level. The mean accuracy over the range of the calibration curve was -4.2% and the detection limit was 0.15 microg/ml. The assay was successfully applied to bovine plasma following intramuscular injection of ceftiofur sodium. This simplified method is suitable for pharmacokinetic applications involving ceftiofur at normal therapeutic levels.

Topics: Animals; Biotransformation; Calibration; Cattle; Cephalosporins; Chromatography, High Pressure Liquid; Injections, Intramuscular; Magnetic Resonance Spectroscopy; Reference Standards; Reproducibility of Results; Solutions; Spectrophotometry, Ultraviolet

The objective of this study was to evaluate the stability of ceftiofur (1 mg mL(-1)) in aqueous solutions at various pH (1, 3, 5, 7.4 and 10) and temperature (0, 8, 25, 37 and 60 degrees C) conditions. The ionic strength of all these solutions was maintained at 0.5 M. Ceftiofur solutions at pH 5 and 7.4 and in distilled water (pH = 6.8) were tested at all the above temperatures. All other solutions were tested at 60 degrees C. Over a period of 84 h, the stability was evaluated by quantifying ceftiofur and its degradation product, desfuroylceftiofur, in the incubation solutions. HPLC was used to analyse these compounds. At 60 degrees C, the rate of degradation was significantly higher at pH 7.4 compared with pH 1, 3, 5 and distilled water. At both 60 degrees C and 25 degrees C, degradation in pH 10 buffer was rapid, with no detectable ceftiofur levels present at the end of 10 min incubation. Degradation rate constants of ceftiofur were 0.79+/-0.21, 0.61+/-0.03, 0.44+/-0.05, 1.27+/-0.04 and 0.39+/-0.01 day(-1) at pH 1, 3, 5, 74 and in distilled water, respectively. Formation of desfuroylceftiofur was the highest (65%) at pH 10. The rate of degradation increased in all aqueous solutions with an increase in the incubation temperature. At pH 7.4 the degradation rate constants were 0.06+/-0.01, 0.06+/-0.01, 0.65+/-0.17, and 1.27+/-0.05 day(-1) at 0, 8, 25, 37 and 67 degrees C, respectively. The energy of activation for ceftiofur degradation was 25, 42 and 28 kcal mol(-1) at pH 5, 7.4 and in distilled water, respectively. Desfurylceftiofur formation was the greatest at alkaline pH compared with acidic pH. Ceftiofur degradation accelerated the most at pH 7.4 and was most rapid at pH 10. The results of this study are consistent with rapid clearance of ceftiofur at physiological pH.

Topics: Cephalosporins; Drug Stability; Hydrogen-Ion Concentration; Temperature; Water

The metabolism of ceftiofur in bovine kidney, liver, muscle and lung, and the effects of the presence of cystine and glutathione in the media were evaluated using S-9 and microsomal tissue fractions. Conversion of ceftiofur to desfuroylceftiofur (DFC) was catalyzed by an esterase which was most active in kidney, followed by liver. It was not very active in muscle and lung. After DFC was liberated, it rapidly bound primarily to tissue proteins (> 56%), and was also conjugated to cysteine and glutathione. Production of DFC-cysteine by disulfide exchange of DFC with cystine and production of DFC-glutathione by conjugation of DFC to glutathione occurred in buffer if glutathione and cystine were present in the medium. These conjugations were also observed in incubations with tissue fractions, indicating that they were not inhibited by the tissues endogenous molecules. In addition, the metabolism of DFC-glutathione to DFC-cysteine was observed when tissue proteins were present. The metabolism of DFC-glutathione to DFC-cysteine was faster in kidney than in liver. Metabolites devoid of an intact beta-lactam ring were not observed in these in vitro studies.

Topics: Animals; Cattle; Cephalosporins; Cystine; Glutathione; In Vitro Techniques; Kidney; Liver; Lung; Male; Microsomes, Liver; Muscles; Subcellular Fractions; Time Factors

Ceftiofur (XNL) and its primary metabolite, desfuroylceftiofur (DXNL), were evaluated for in vitro activity against 539 isolates from veterinary sources. Actinobacillus pleuropneumoniae, Pasteurella spp., Haemophilus somnus, Salmonella spp., Escherichia coli, staphylococci, and streptococci were tested. Overall, XNL and DXNL were equivalent in activity against the gram-negative organisms with all minimum inhibitory concentrations (MICs) within 1 serial dilution. Against the staphylococci, MIC difference of 2-3 serial dilutions were detected with an MIC90 for XNL and DXNL of 1.0 and 4.0-8.0 micrograms/ml, respectively. Although the MIC90 obtained for Streptococcus suis for each compound was within 1 dilution, the MIC values against individual strains were 2-3 dilutions greater for DXNL than for XNL. The MICs obtained with the bovine and equine streptococci for DXNL (MIC90 = 0.03 microgram/ml) were 5 serial dilutions higher than those obtained for XNL (MIC90 < or = 0.0019). Although DXNL was less active than XNL against the streptococci, these differences were not clinically important because both XNL and DXNL were highly active for these bacteria. Although these differences are of little importance with the streptococci, they may have important implications for susceptibility testing of the staphylococci. In conclusion, with the exception of the staphylococci, both XNL and DXNL were highly active against the organisms tested, with MICs for both compounds several fold lower than plasma levels achieved during dosing of XNL.

Topics: Actinobacillus pleuropneumoniae; Animals; Bacterial Infections; Cattle; Cephalosporins; Escherichia coli; Haemophilus; Microbial Sensitivity Tests; Pasteurella; Salmonella; Staphylococcus; Streptococcus

The effect of bacterial infection on antibiotic activity and penetration of parenterally administered ceftiofur into implanted tissue chambers was studied in cattle. Tissue chambers were implanted subcutaneously in the paralumbar fossae of eight calves (256-290 kg body weight). Approximately 80 days after implantation, the two chambers on one side of each animal were inoculated with Pasteurella haemolytica (10(6) CFU/chamber). Eighteen hours after inoculation, ceftiofur sodium was administered intravenously (5 mg/kg) to each of the calves. Non-infected chamber fluid, infected chamber fluid and heparinized blood samples were collected immediately before and at 1, 3, 6, 12 and 24 h after drug administration. Concentrations of ceftiofur and desfuroylceftiofur metabolites and ceftiofur-equivalent microbiological activity were measured by high-pressure liquid chromatography and microbiological assay respectively. Concentrations of ceftiofur and desfuroylceftiofur metabolites and anti-microbial activity in P. haemolytica-infected tissue chambers were significantly higher than those in non-infected tissue chambers at all sampling times, indicating that ceftiofur, regardless of the method used for analysis, localizes at higher concentrations at tissue sites infected with P. haemolytica. Antibiotic activity-concentration ratios were lower in plasma and infected chamber fluid compared with non-infected chamber fluid, suggesting that antibiotic was bound to proteins. However, higher antimicrobial activity in the infected chamber fluid compared with the non-infected chamber fluid, suggests that active drug is reversibly bound to proteins. Protein-bound desfuroylceftiofur may represent a reservoir for release of active drug at the site of infection in the animal.

Topics: Animals; Cattle; Cattle Diseases; Cephalosporins; Chromatography, High Pressure Liquid; Diffusion Chambers, Culture; Dose-Response Relationship, Drug; Injections, Intravenous; Pasteurella Infections; Protein Binding; Software

The effects of maturation on the intravenous (IV) and intramuscular (IM) pharmacokinetics of ceftiofur sodium following a dose of 2.2 mg ceftiofur equivalents/kg body weight were evaluated in 16 one-day-old Holstein bull calves (33-53 kg body weight initially; Group 1) and 14 six-month-old Holstein steers (217-276 kg body weight initially; Group 2). Group 1 calves were fed unmedicated milk replacer until 30 days of age and were then converted to the same roughag/concentrate diet as Group 2. Groups 1-IV and 2-IV received ceftiofur sodium IV, and Groups 1-IM and 2-IM received ceftiofur sodium IM. Group 1 calves were dosed at 7 days of age and at 1 and 3 months of age; group 2 calves were dosed at 6 and 9 months of age. Blood samples were obtained serially from each calf, and plasma samples were analysed using an HPLC assay that converts ceftiofur and all desfuroylceftiofur metabolites to desfuroylceftiofur acetamide. Cmax values were similar in all calves, and were no higher in younger calves than in older calves. Plasma concentrations remained above 0.150 microgram ceftiofur free acid equivalents/mliter for 72 h in 7-day-old calves, but were less than 0.150 microgram/mliter within 48 h following IV or IM injection for 6- and 9-month-old calves. Intramuscular bioavailability, assessed by comparing the model-derived area under the curve (AUCmod) from IM and IV injection at each age, appeared to be complete. After IV administration, the AUCmod in 7-day-old and 1-month-old calves (126.92 +/- 21.1 micrograms.h/mliter and 135.0 +/- 21.6 micrograms.h/mliter, respectively) was significantly larger than in 3-, 6- and 9-month-old calves (74.0 +/- 10.7 micrograms.h/mliter, 61.0 +/- 17.7 micrograms.h/mliter and 68.5 +/- 12.8 micrograms.h/mliter, respectively; P < 0.0001). The Vd(ss) decreased linearly within the first 3 months of life in cattle (0.345 +/- 0.0616 L/kg, 0.335 +/- 0.919 L/kg and 0.284 +/- 0.0490 L/kg, respectively; P = 0.031), indicative of the decreasing extracellular fluid volume in maturing cattle. The ClB was significantly smaller in 7-day-old and 1-month-old calves (0.0178 +/- 0.00325 L/h.kg and 0.0167 +/- 0.00310 L/h.kg, respectively) than in 3-, 6- and 9-month-old calves (0.0303 +/- 0.0046 L/h.kg, 0.0398 +/- 0.0149 L/h.kg and 0.0330 +/- 0.00552 L/h.kg, respectively; P < or = 0.001). This observation may be indicative of maturation of the metabolism and/or excretion processes for ceftiofur and desfuroylceftiofur metabolites. The approved dosage reg

Topics: Aging; Analysis of Variance; Animals; Animals, Newborn; Biological Availability; Cattle; Cephalosporins; Chromatography, High Pressure Liquid; Injections, Intramuscular; Injections, Intravenous; Jugular Veins; Male; Models, Biological; Random Allocation; Reference Standards; Regression Analysis

An HPLC method was developed and validated for the determination of ceftiofur-related metabolites that have the potential to be microbiologically active in swine muscle, kidney, liver and fat. Its performance was evaluated against incurred-residue swine tissues. This method is based on the cleavage of the disulfide and/or thioester bonds between the metabolites and their conjugate sulfur containing moiety using dithioerythritol to yield desfuroylceftiofur, and further stabilization to desfuroylceftiofur acetamide. The limit of quantitation was 0.1 micrograms ceftiofur equivalents/g tissue. The assay is specific for ceftiofur-related metabolites when evaluated against commercially available antibiotics for swine.

Topics: Adipose Tissue; Animals; Cephalosporins; Chromatography, High Pressure Liquid; Female; Kidney; Liver; Male; Muscles; Sensitivity and Specificity; Swine

Ceftiofur sodium, a broad spectrum cephalosporin antibiotic approved for veterinary use, is metabolized to desfuroylceftiofur which is conjugated to micro as well as macromolecules. Twelve horses, weighting 442-618 kg, were injected intramuscularly with a single dose of 2.2 mg ceftiofur/kg (1.0 mg/lb) body weight. Blood was collected at various intervals over 24 h after treatment. Three groups of four horses each were euthanized and lungs were collected at 1, 12, and 24 h after treatment. The concentration of desfuroylceftiofur and desfuroylceftiofur conjugates in the plasma and lungs was determined by converting them to desfuroylceftiofur acetamide (DCA) and measured DCA by high performance liquid chromatography with UV detection. The average maximum concentration (Cmax) of desfuroylceftiofur and related metabolites in plasma expressed as ceftiofur equivalents was 4.46 +/- 0.93 micrograms/ml occurred at 1.25 +/- 0.46 h after treatment. These concentrations declined to 0.99 +/- 0.16, 0.47 +/- 0.15 and 0.17 +/- 0.02 microgram/ml at 8, 12, and 24 h, respectively. The mean residence time of ceftiofur metabolites was 6.10 +/- 1.27 h. Concentrations of desfuroylceftiofur and desfuroylceftiofur conjugates in the lungs of horses expressed as ceftiofur equivalents were 1.40 +/- 0.36, 0.27 +/- 0.07, and 0.15 +/- 0.08 micrograms/ml at 1, 12, and 24 h, respectively. These concentrations of the drug at 12 and 24 h in lung homogenate were similar but slightly lower than plasma concentrations in the same horses, and the plasma pharmacokinetic values including half-life were similar to those observed at the approved dose of 1.1-2.2 mg ceftiofur/kg body weight administered intramuscularly once daily for 3-5 days in cattle.

Topics: Animals; Cephalosporins; Chromatography, High Pressure Liquid; Female; Half-Life; Horses; Injections, Intramuscular; Lung; Male; Tissue Distribution

A simple and sensitive liquid chromatographic method has been developed for the simultaneous determination of ceftiofur and its metabolite desfuroylceftiofur in bovine serum and milk. The method involved an ultrafiltration of diluted serum/milk with an equal volume of 50% acetonitrile through a 10,000 dalton molecular mass cut-off filter. Separation of ceftiofur and desfuroylceftiofur from the other serum/milk components was performed by ion-paired (octane and dodecanesulfonate) liquid chromatography using a reversed-phase column eluted with acetonitrile-water solution. The ultraviolet-visible absorbance of the column effluent was monitored in 200-350 nm range of a photodiode-array detector or at lambda max 289.6 nm for ceftiofur, lambda max 265.8 nm for desfuroylceftiofur and lambda max 271.4 nm for dimer of desfuroylceftiofur. Recoveries of ceftiofur from bovine milk spiked with 1 and 10 micrograms/ml were 95.9 and 97.0% with coefficients of variation of 3.69 and 2.51%, respectively. Recovery of ceftiofur from bovine serum spiked with 10 micrograms/ml was 90.4% with a coefficient of variation of 5.29%. A correlation coefficient of 0.9992 occurred with ceftiofur in aqueous solutions (n = 5, in duplicates). The limit of detection was estimated to be approximately 50 ppb (ng/ml). Additionally, this paper documents the presence of a ceftiofur metabolite in bovine serum under in vitro and in vivo conditions. The metabolite was identified as desfuroylceftiofur together with its dimer 3,3'-desfuroylceftiofur disulfide by thermospray liquid chromatography-mass spectrometry.

Topics: Animals; Cattle; Cephalosporins; Chromatography, Liquid; Female; Ions; Mass Spectrometry; Milk; Reproducibility of Results; Spectrophotometry, Ultraviolet