Pharmacokinetics and lung and muscle concentrations of tulathromycin following subcutaneous administration in white-tailed deer (Odocoileus virginianus).

Respiratory tract infections are common in farmed North American white-tailed deer (Odocoileus virginianus). Tulathromycin is approved for use in cattle but not deer but is often employed to treat deer. The pharmacokinetic properties and lung and muscle concentrations of tulathromycin in white-tailed deer were investigated. Tulathromycin was administered to 10 deer, and then, serum, lung, and muscle tulathromycin concentrations were measured using liquid chromatography-mass spectrometry (LC-MS). The mean maximal serum tulathromycin concentration in deer was 359 ng/mL at 1.3 h postinjection. The mean area under the serum concentration-time curve, apparent volume of distribution, apparent clearance, and half-life was 4883 ng·h/mL, 208 L/kg, 0.5 L/h/kg, and 281 h (11.7 days), respectively. The maximal tulathromycin concentration in lung and muscle homogenate from a single animal was 4657 ng/g (14 days) and 2264 ng/g (7 days), respectively. The minimum concentrations in lung and muscle were 39.4 ng/g (56 days) and 9.1 ng/g (56 days), respectively. Based on similarity in maximal serum concentrations between deer and cattle and high lung concentrations in deer, we suggest the recommended cattle dosage is effective in deer. Tissue concentrations persisted for 56 days, suggesting a need for longer withdrawal times in deer than cattle. Further tissue distribution and depletion studies are necessary to understand tulathromycin persistence in deer tissue; clinical efficacy studies are needed to confirm the appropriate dosage regimen in deer.

Pharmacokinetics of tulathromycin after subcutaneous injection in North American bison (Bison bison).

Tulathromycin is approved for the treatment of respiratory disease in cattle and swine. It is intended for long-acting, single-dose injection therapy (Draxxin), making it particularly desirable for use in bison due to the difficulty in handling and ease of creating stress in these animals. The pharmacokinetic properties of tulathromycin in bison were investigated. Ten wood bison received a single 2.5 mg/kg subcutaneous injection of Draxxin. Serum concentrations were measured by liquid chromatography-mass spectrometry (LC-MS) detection. Tulathromycin demonstrated early maximal serum concentrations, extensive distribution, and slow elimination characteristics. The mean maximum serum concentration (Cmax) was 195 ng/mL at 1.04 h (tmax) postinjection. The mean area under the serum concentration-time curve, extrapolated to infinity (AUC0-inf ), was 9341 ng · h/mL. The mean apparent volume of distribution (Vd /F) and clearance (Cls/F) was 111 L/kg and 0.4 L/h/kg, respectively, and the mean half-life (t1/2) was 214 h (8.9 days). Compared to values for cattle, Cmax and AUC0-inf were lower in bison, while the Vd /F was larger and the t1/2 longer. Tissue distribution and clinical efficacy studies in bison are needed to confirm the purported extensive distribution of tulathromycin into lung tissue and to determine whether a 2.5 mg/kg subcutaneous dosage is adequate for bison.

Kinetics and residues after intraperitoneal procaine penicillin G administration in lactating dairy cows.

This paper describes the pharmacokinetic profile of procaine penicillin G after intraperitoneal (IP) administration in eight lactating dairy cows. Procaine pencillin G (PPG, 21 000 IU/kg) was deposited into the abdominal cavity of each cow following an incision in the right paralumbar fossa. Blood and milk samples were taken over the following 10 days, at which point the cows were euthanized. Plasma, milk, muscle, liver, and kidney penicillin concentrations were determined by HPLC, with a limit of quantification of 5 ng/mL for plasma and milk and 40 ng/g for tissue samples. A noncompartmental method was used to analyze plasma kinetics. The mean pharmacokinetic parameters (+/-SD) were: C(max), 5.5 +/- 2.6 microg/mL; T(max), 0.75 +/- 0.27 h; AUC(0-infinity), 10.8 +/- 4.9 microg x h/mL; MRT, 2.2 +/- 0.9 h. All milk from treated cows contained detectable penicillin residues for a minimum of three milkings (31 h) and maximum of five milkings (52 h) after administration. Concentrations of penicillin in all muscle, liver, and kidney samples taken 10 days postadministration were below the limit of quantification. Necropsy examinations revealed foci of hemorrhage on the rumenal omentum of most cows but peritonitis was not observed. Systemic inflammation as determined by change in leukogram or plasma fibrinogen was noted in one cow. The results of this study demonstrate that IP PPG is absorbed and eliminated rapidly in lactating dairy cows.

Pharmacokinetics of tilmicosin in equine tissues and plasma.

The macrolide antibiotic tilmicosin has potential for treating bacterial respiratory tract infections in horses. A pharmacokinetic study evaluated the disposition of tilmicosin in the horse after oral (4 mg/kg) or subcutaneous (s.c.) (10 mg/kg) administration. Tilmicosin was not detected in equine plasma or tissues after oral administration at this dose. With s.c. injection, tilmicosin concentrations reached a maximum concentration of approximately 200 ng/mL in the plasma of the horses. Tilmicosin concentrations in plasma persisted with a mean residence time (MRT) of 19 h. Maximum tissue residue concentrations (C(max)) of tilmicosin measured in equine lung, kidney, liver and muscle tissues after s.c. administration were 2784, 4877, 1398, and 881 ng/g, respectively. The MRT of tilmicosin in these tissues was approximately 27 h. Subcutaneous administration of tilmicosin resulted in severe reactions at the injection sites.

Determination of the performance characteristics of a new multi-residue method for non-steroidal anti-inflammatory drugs, corticosteroids and anabolic steroids in food animal tissues.

A new LC-MS/MS method was developed for the analysis of 29 veterinary drug residues, spanning three different drug classes, in animal tissues. The procedures used to measure the characteristic performance parameters of the method and the results obtained using fortified blank bovine muscle and kidney tissue are described. For a quantitative and confirmatory method, the characteristic performance parameters to be determined are the limits of quantification, trueness, recovery, precision, selectivity, ruggedness, and stability. The characteristic performance parameters defined for the method will be verified during a validation study by an independent experienced analyst to determine whether the method is suitable for use in a regulatory monitoring and control program for residues of the 29 analytes.

Tissue disposition and depletion of penicillin G after oral administration with milk in unweaned dairy calves.

OBJECTIVE: To determine tissue depletion of penicillin G in calves after oral ingestion with milk replacer and estimate a withdrawal period. DESIGN: Longitudinal controlled trial. ANIMALS: 26 Holstein calves. PROCEDURE: Once daily, 24 calves were fed milk replacer containing procaine penicillin G (0.68 mg/kg [0.31 mg/lb] of body weight); 2 calves served as controls. After 1 feeding, 12 calves were euthanatized in groups of 3 each 4, 6.5, 9.5, and 13 hours after feeding. After 14 days, 12 calves were euthanatized in groups of 3 each 4, 6.5, 9.5, and 13 hours after the final feeding. Concentrations of penicillin G were determined in tissues, blood, and urine by use of high-performance liquid chromatography. RESULTS: Penicillin G was not detected in muscle samples of treated calves. The highest concentrations of penicillin G in plasma, kidney, and liver were 13 ng/ml, 92 ng/g, and 142 ng/g, respectively. Thirteen carcasses had violative drug residues; 12 had violative residues in the liver only, and 1 had violative residues in the liver and kidney. A 21-hour withdrawal period was estimated. CONCLUSIONS AND CLINICAL RELEVANCE: Liver had the highest concentration of penicillin G and was most likely to have violative residues. Feeding calves milk containing penicillin G has the potential to cause violative drug residues in tissues. It is recommended to observe an appropriate withdrawal time prior to slaughter if calves are fed milk from cows treated with penicillin G.

Determination of flunixin residues in bovine muscle tissue by liquid chromatography with UV detection.

A new and sensitive liquid chromatography-ultra violet method with a detection limit of 6 ng/g (ppb) and a limit of quantification of 15 ng/g was developed for the determination of flunixin residues in bovine muscle tissue. Flunixin in homogenized animal tissue was extracted with acetonitrile after enzyme digestion. The tissue digest (extract) was then cleaned up on a solid-phase extraction cartridge and eluted with acidified hexane. After the eluate was evaporated to dryness under nitrogen at 55 degrees C, the residue was reconstituted in 1 mL mobile phase solution and analyzed by reversed-phase gradient chromatography with UV detection at 285 nm. The method was then applied in a survey study of slaughter animals to determine whether flunixin is being used in an off-label manner for veal and beef production in Canada.

Multiresidue liquid chromatographic method for determining residues of mono- and dibasic penicillins in bovine muscle tissues.

A liquid chromatographic method with UV detection at 325 nm was developed for simultaneous determination of amoxicillin, ampicillin, penicillin G, and cloxacillin residues in bovine muscle tissue as their mercaptide derivatives. The penicillins are extracted from bovine tissues with 0.1 M phosphate buffer (pH 8.5), cleaned up on a t-C18 Sep-Pak cartridge, and eluted with 2 mL acetonitrile. After the acetonitrile in the eluate is evaporated to dryness, the residue is dissolved in 200 microL (40 + 60, v/v) acetonitrile-phosphate buffer (pH 6.5) and derivatized with acetic anhydride and mercuric chloride in the presence of 1,2,4-triazole at 65 degrees C for 30 min. Gradient analysis on a Spherisorb 5 microns ODS(2) (octadecyl silane) analytical column using a binary mobile phase consisting of acetonitrile and 0.10 M phosphate buffer (pH 6.5) in the presence of 0.0157 M sodium thiosulfate at 1 mL/min permits determination of each intact penicillin in bovine muscle tissue at > or = 10 ppb with recoveries > or = 72%. This laboratory method provides detection sensitivities equivalent to those of rapid tests used for screening beta-lactam drug residues in bovine tissue samples for regulatory enforcement.

Improvement in the multiresidue liquid chromatographic analysis of residues of mono- and dibasic penicillins in bovine muscle tissues.

A recently developed multiresidue method using gradient liquid chromatographic conditions for analysis of residues of beta-lactam drugs in bovine muscle tissues after precolumn derivatization with acetic anhydride was modified to permit isocratic analysis. The modification included replacing the acylating reagent, acetic anhydride, with benzoic anhydride and increasing sample size for extraction from 2 to 3 g. The modifications have reduced analysis time per sample from > 1 h to about 22 min without loss in detection sensitivities for the beta-lactams, resulting in a significant increase in the number of samples that can be analyzed in 1 day from 1 to 8. The modifications make the multiresidue LC method more suitable than the original method for use in regulatory programs for routine analysis of these veterinary drug residues in bovine muscle tissues.

Characteristics of the LacTek test as applied to tissue samples: assessment of performance using incurred field samples.

The Lactek test, marketed for antimicrobial residue detection in milk, was validated for the detection of antimicrobial residues in tissues. A previous study found that the LacTek test could confidently identify tissue samples spiked with antimicrobial residues. However, the test could not reliably distinguish violative from nonviolative spiked samples relative to Canadian maximum residue limits (MRLs). The objectives of this study were to assess and compare the performance of the LacTek tests for beta-lactams, tetracyclines, gentamicin, and sulfamethazine on samples containing naturally incurred residues by running the test in parallel with the standard microbial inhibition test (MIT) presently used for the routine testing of tissues at our facility and to assess the agreement with high pressure liquid chromatographic (HPLC) determinative methods. Parallel testing with the official MIT found that the Lactek tests could be confidently used for testing tissue samples containing incurred residues. Among 1,008 MIT-positive samples, the LacTek test found that 90% contained beta-lactams and/or tetracyclines. A further 7.3% of violative residues could not be identified to an antimicrobial class. In addition, 9% of samples testing negative on the MIT were found to contain an antimicrobial residue by the LacTek tests. Comparative testing with HPLC methods found that there was very good agreement between the two tests and that most violations were due to penicillin G and oxytetracycline. Although the LacTek test cannot be used to distinguish violative from nonviolative residue levels, it does offer several advantages over the present MIT. These include speed, ease of use, the ability to identify residues to a specific class, and an improved sensitivity at the MRL level for the most commonly found antimicrobials in tissue.

Bacterial inhibition tests used to screen for antimicrobial veterinary drug residues in slaughtered animals.

Bacterial inhibition tests used to screen milk, tissues, blood, and urine for antimicrobial veterinary drug residues must be high volume, quick, rugged, inexpensive, and sensitive. Bacterial inhibition tests--such as the Swab Test on Premises (STOP), the Calf Antibiotic and Sulfa Test (CAST), the Fast Antibiotic Screen Test (FAST), the Charm Farm Test (CFT), the Antimicrobial Inhibition Monitor 96 (AIM-96) assay, the German Three Plate Test, the European Union Four Plate Test and the New Dutch Kidney Test--have been used to screen tissues for antimicrobial activity. The CFT and the Brilliant Black Reduction Test (BBRT) also have been used to screen plasma. The Live Animal Swab Test (LAST) was developed to screen urine. This review examines the use and limitations of these screening tests for regulatory control and avoidance of veterinary drug residues in meat. The ideal bacterial inhibition test for screening antimicrobial residues in slaughtered animals does not exist. Each of the current and potential tests has limitations.

Simultaneous determination of six penicillins in cows' raw milk by a multiresidue high-performance liquid chromatographic method.

A high-performance liquid chromatographic method based on C18 solid-phase extraction and ultraviolet detection at 323 nm of analytes derivatized with benzoic anhydride and 1,2,4-triazole mercuric chloride solution was developed for the simultaneous determination of amoxicillin, penicillin G (benzylpenicillin), ampicillin, oxacillin, cloxacillin and dicloxacillin residues in raw milk. The detection limit of the method was 1.3 microg/l for penicillin G; 1.4 microg/l for amoxicillin, oxacillin and cloxacillin, 1.5 microg/l for ampicillin and 2.7 microg/l for dicloxacillin. The mean recovery was 95-102% for amoxicillin, penicillin G and ampicillin, 92-98% for oxacillin and cloxacillin and 87-94% for dicloxacillin, measured by using an internal standard. The relative repeatability standard deviation was 4-9% on level 4-15 micro/l, respectively, 2-7% on level 30-40 microg/l.

Determination of trimethoprim and sulphadoxine residues in porcine tissues and plasma.

Healthy gilts and market-ready hogs were administered a single intramuscular (IM) injection of Borgal, a commercial formulation of trimethoprim-sulfadoxine (TMP-SDX), once or twice daily. The objectives were to determine if a newly-developed high-performance liquid chromatographic (HPLC) method would be suitable for measuring the residual concentrations of TMP in the plasma of these live animals, and to determine if the administration of this veterinary drug would leave measurable residues in their plasma and tissues at slaughter. Plasma and tissue concentrations of SDX and TMP from these animals were determined over a period of 14 d using thin-layer chromatography/densitometry (TLCD), and the newly-developed HPLC method, respectively. The lowest detectable limit (LDL) for SDX in plasma and tissue was 20 ppb by TLCD. The HPLC method had a LDL of 5 ppb for TMP in plasma and tissue. Both methods were then used to provide baseline data on the absorption and depletion of TMP and SDX from these healthy animals. It was observed that both TMP and SDX were readily absorbed into the blood and tissues, but TMP was eliminated much faster than SDX. No TMP residues were detected in the plasma of any of the gilts at and beyond 21 h after drug administration. Also, no TMP residues were detected in the plasma of any of the market-ready hogs 24 h after drug administration at either the label dose or twice the label dose. Sulfadoxine residues at concentrations above the maximum residue limit (MRL) of 100 ppb were, however, detected in the plasma, muscle, kidney, liver, and injection sites of hogs slaughtered 1 and 3 d after a single IM administration at the label dose. Although SDX residues were still detectable in the lungs, kidney, liver and plasma of some hogs 10 d after administration of the label dose and twice the label dose, these were below the MRL. Postmortem examination revealed necrosis and inflammation at the injection sites, but no visible deposits of the injected drug.

Comparison of four commercially available rapid test kits with liquid chromatography for detecting penicillin G residues in bovine plasma.

Four commercially available rapid tests (Brilliant Black reduction test, LacTek test, Charm Farm test, and Charm Test II receptor assay) were compared with a liquid chromatographic (LC) method (lowest quantitatable level of 5 ng/mL) in their efficiency, reliability, and sensitivity to detect penicillin G in bovine plasma. Samples were obtained from 16 steers treated with procaine penicillin G alone or in combination with its long-acting form, benzathine penicillin G. The steers were injected intramuscularly with penicillin G doses ranging from label dose to about 9 times label dose. When results of the Brilliant Black reduction, LacTek, Charm Test II, and Charm Farm tests for penicillin G in plasma (with detection sensitivities of 5, 10, 20, and 30 ng/mL, respectively) were compared with results of LC, none of the rapid tests gave false-positive results. Each rapid test elicited a positive response when used to test bovine plasma containing penicillin G residues at concentrations above the test's detection sensitivity. The simplicity, selectivity, and sensitivity of the rapid tests, coupled with rapidity with which results are obtained, make them suitable for use in large-volume preslaughter screening of penicillin-treated cattle.

Determination of sulfadimethoxine and sulfamethazine residues in animal tissues by liquid chromatography and thermospray mass spectrometry.

A simple, sensitive, and rapid method for simultaneous determination of sulfamethazine and sulfadimethoxine residues in animal tissues by liquid chromatography (LC) with on-line confirmation by thermospray mass spectrometry is reported. Tissue extracts, after cleanup on C18 cartridges, were injected into a reversed-phase C18 column, and the sulfa drugs were determined by ultraviolet (UV) detection at 265 nm. On-line confirmation of sulfamethazine and sulfadimethoxine in the extracts by mass spectrometry was obtained by feeding the sulfa drugs eluting from the chromatographic column after UV detection directly into the ion source of a mass spectrometer with a thermospray ionization LC interface. Analytical results obtained with the LC method, which has detection limits of 2 and 10 ng/g of tissue, for sulfamethazine and sulfadimethoxine, respectively, compared favorably with those obtained with the official thin-layer chromatographic-densitometric method.

Disposition of penicillin G after administration of benzathine penicillin G, or a combination of benzathine penicillin G and procaine penicillin G in cattle.

Plasma concentration of penicillin G was evaluated in beef steers after administration of either a combination of benzathine penicillin G and procaine penicillin G in a 1:1 mixture at a dosage of 9,000 U/kg of body weight, IM (n = 5), 24,000 U/kg, IM (n = 5), or 8,800 U/kg, SC (n = 5), or benzathine penicillin G alone at a dosage of 12,000 U/kg, IM (n = 7). Plasma concentration of penicillin G was measured by use of a high-performance liquid chromatography assay that had a limit of determination of 0.005 microgram/ml. At a dosage for this combination of 9,000 U/kg IM, and 8,800 U/kg, SC, which are approved label recommendations in Canada, and the United States, respectively, mean (+/- SEM) peak plasma concentration was 0.58 (+/- 0.15) and 0.44 (+/- 0.02) microgram/ml, respectively. Although plasma penicillin concentration was quantifiable for 7 days in the steers that received 9,000 U/kg, IM, and for 4 days in the steers that received 8,800 U/kg, SC, the concentration was < 0.1 microgram/ml in both groups after the first 12 hours. After administration of the combination at dosage of 24,000 U/kg, IM, there was an initial peak plasma concentration at approximately 2 hours; thereafter, plasma concentration decreased slowly, with half-life of 58 hours. Although plasma penicillin G concentration was quantifiable for 12 days at this dosage, concentration was < 0.1 microgram/ml after the first 48 hours. After the initial 48 hours, plasma concentration of penicillin was of similar magnitude and decreased at similar rate for the combination at dosage of 24,000 U/kg and for 12,000 U/kg of benzathine penicillin G alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of penicillin G in milk by liquid chromatography.

A liquid chromatographic (LC) method that was previously developed for penicillin G residues in animal tissues has been adapted to milk and milk products. After protein precipitation with sodium tungstate, samples are applied to a C18 solid-phase extraction cartridge, from which penicillin is eluted, derivatized with 1,2,4-triazole-mercuric chloride solution, and analyzed by isocratic liquid chromatography (LC) on a C18 column with UV detection at 325 nm. Quantitation is done with reference to penicillin V as an internal standard. Penicillin G recoveries were determined to be > 70% on standards fortified at 3-60 ppb. Accuracy approached 100% using the penicillin V internal standard. The detection limit for penicillin G residues was 3 ppb in fluid milk. Samples may be confirmed by thermospray/LC at concentrations approaching the detection limit of the UV method.