Quality of amoxicillin/clavulanic acid oral formulations for intended veterinary use in the UK, Malaysia, Serbia and Thailand.

OBJECTIVES: Amoxicillin/clavulanate is the most commonly used oral antimicrobial drug in companion animals. The objective of the study was to detect types and frequency of deficits in the quality of veterinary oral formulations of amoxicillin/clavulanate in various countries. MATERIALS AND METHODS: In a prospective study with purposive sampling, amoxicillin/clavulanate tablet formulations for canine use were collected in four countries (wholesalers or veterinary practice) and shipped to a central bioanalytical laboratory. Twenty-four samples were collected from the UK (nine), Malaysia (nine), Serbia (four) and Thailand (two), yielding 18 different formulations (10 veterinary). Packaging inspection, tablet disintegration and content assay were conducted (validated high-performance liquid chromatography with ultra-violet detection); content was acceptable when within the 90% to 120% pre-specified range (US Pharmacopeia). RESULTS: Secondary packaging was present for 13 of 24 samples and primary packaging integrity was verified for all but one sample. Amoxicillin trihydrate/potassium clavulanate label ratio was 4:1, except for three formulations (2:1). Tablet dose strength ranged from 250 to 625 mg. All formulations contained both analytes. For amoxicillin, two of 24 samples were out of specification with 72.8% (Malaysia) and 82.3% (Thailand) of labelled content. For clavulanate, four of 24 samples were out of specification with 46.9% (Serbia), 79.0% (UK), 84.3% (Serbia) and 86.5% (Thailand) of labelled content. One formulation (Thailand) failed for both analytes. CLINICAL SIGNIFICANCE: Antimicrobial formulations of substandard quality have negative consequences for efficacy in patients and potentially promote antimicrobial resistance. There was evidence of substandard formulations in all countries, not only for amoxicillin but especially for clavulanate; this could compromise equitable access to acceptable quality essential veterinary medicines worldwide.

Antimicrobial use and stewardship practices on Australian beef feedlots.

OBJECTIVE: Improving antimicrobial stewardship in the livestock sector requires an understanding of the motivations for antimicrobial use and the quantities consumed. However,detailed information on antimicrobial use in livestock sectors is lacking. This cross-sectional study aimed to better understand antimicrobial use in the beef feedlot sector in Australia. DESIGN: A self-administered questionnaire asking about antimicrobial use and reasons for use was designed and mailed to beef feedlot operators in Australia. Respondents were asked to report the percentage of animals treated, purpose of use, and disease conditions targeted for 26antimicrobial agents. RESULTS: In total, 83 of 517 (16.1%) beef feedlot operators completed the survey. Monensin (61.0%of respondents) and virginiamycin (19.5%of respondents) were the most commonly reported in-feed antimicrobials. In-feed antimicrobial agents were most frequently used by respondents for treatment of gastrointestinal diseases (52.8%). Antimicrobials were used for growth promotion by 42.1% of respondents, with most (85.7%) reporting the use of ionophores(a group of compounds not used in human medicine). Short-acting penicillin(69.1%), short-acting oxytetracycline, and tulathromycin (both 57.3%) werethe most common injectable antimicrobial agents used. Injectable antimicrobials were most frequently used to treat respiratory (72.3%) and musculoskeletal (67.5%) conditions. CONCLUSION: Overall,the use of antimicrobials was appropriate for the purpose indicated, and there was a strong preference for drugs of low-importance in human medicine. The data described here stand to be a strong influence on the implementation of an antimicrobial stewardship program in the sector.

Preliminary investigations into a novel, long-acting, injectable, intramuscular formulation of omeprazole in the horse.

BACKGROUND: Pilot investigations have suggested that a novel, long-acting, injectable i.m. formulation of omeprazole (LA-OMEP) can induce acid suppression for up to 7 days following a single injection. OBJECTIVES: To investigate the pharmacodynamics and assess the clinical efficacy of the LA-OMEP formulation. STUDY DESIGN: Part A comprised a pharmacodynamic study. Part B consisted of a pilot clinical trial. METHODS: Part A enrolled six adult Thoroughbred horses with percutaneous gastrotomy tubes. Intragastric pH was measured for continuous 23-h periods (08.00-07.00 h) for eight consecutive days (days 0-7). A single 2.0-g dose of a 100 mg/mL LA-OMEP formulation was administered at 08.00 h on day 1. In Part B, 26 horses with squamous or glandular gastric disease were enrolled based on routine gastroscopic evaluation. Once enrolled, horses received 2.0 g of the 100 mg/mL LA-OMEP formulation by i.m. injection on days 0 and 7. Repeat gastroscopy was performed on days 14 (23 horses) or 16 (one horse). RESULTS: In Part A, the percentage of time during which pH was above 4 exceeded 66% for days 1-4 in all horses and days 1-7 in four of the six horses studied. In Part B, healing was observed in all 22 (100%, 95% confidence interval [CI] 89-100%) horses with squamous disease and in nine of 12 (75%, 95% CI 47-92%) horses with glandular disease. Improvement, by at least one grade, was observed in all 22 (100%, 95% CI 89-100%) horses with squamous disease and in all 12 (100%, 95% CI 81-100%) horses with glandular disease. No worsening of lesions was observed. Lesion grade decreased over time in both the squamous (P<0.0001) and glandular (P = 0.0024) mucosa. MAIN LIMITATIONS: Small sample sizes. CONCLUSIONS: The results of the present study compare favourably with previous reports on the pharmacodynamics of omeprazole and the clinical outcomes of trials reporting response to oral omeprazole therapy.

Pharmacokinetics and cardiovascular effects following a single oral administration of a nonaqueous pimobendan solution in healthy dogs.

Pimobendan is an inodilator used in the treatment of canine congestive heart failure (CHF). The aim of this study was to investigate the pharmacokinetics and cardiovascular effects of a nonaqueous oral solution of pimobendan using a single-dose, operator-blinded, parallel-dose study design. Eight healthy dogs were divided into two treatment groups consisting of water (negative control) and pimobendan solution. Plasma samples and noninvasive measures of cardiovascular function were obtained over a 24-h period following dosing. Pimobendan and its active metabolite were quantified using an ultra-high-performance liquid chromatography-mass spectrometer (UHPLC-MS) assay. The oral pimobendan solution was rapidly absorbed [time taken to reach maximum concentration (Tmax ) 1.1 h] and readily converted to the active metabolite (metabolite Tmax 1.3 h). The elimination half-life was short for both pimobendan and its active metabolite (0.9 and 1.6 h, respectively). Maximal cardiovascular effects occurred at 2-4 h after a single oral dose, with measurable effects occurring primarily in echocardiographic indices of systolic function. Significant effects persisted for <8 h. The pimobendan nonaqueous oral solution was well tolerated by study dogs.

Effect of an immunomodulatory feed additive on markers of immunity in pasture-fed dairy cows.

BACKGROUND: Infectious diseases in dairy cows often follow a time of nutritional or physiological stress and the subsequent altered immune system function. This study aimed to determine if the immunomodulatory effects of a feed additive previously observed in experimental animals and housed cattle fed total mixed rations could be reproduced in pasture-fed dairy cattle under Australian conditions. METHODS: The study included 34 pasture-fed dairy cattle given the treatment (n = 17) or placebo (bentonite, n = 17) for an acclimation period of 15 days followed by 60 days of supplementation. Blood tests were taken pre-trial and then 30, 60 and 90 days after acclimation. Blood samples were extracted and preserved in Trizol and analysed for immune markers. RESULTS: Pasture-fed dairy cows in the treatment group had significantly higher levels of the immune markers interleukin-8R and L-selectin in comparison with placebo-fed cows at 60 days after the start of supplementation. CONCLUSION: The immunomodulatory effects of the additive observed in the current study and the associated enhanced neutrophil function demonstrated by other studies suggest a role in decreasing the rates of mastitis and other infectious diseases of dairy cattle, particularly during times of nutritional or physiological stress.

Antimicrobial resistance in animal and public health: introduction and classification of antimicrobial agents.

Bacteria have a remarkable ability to adapt, evolve and survive by developing resistance to therapeutic compounds. This ability is also shared by other pathogenic agents such as viruses, fungi, and parasites. Even when focusing on bacterial resistance only, this phenomenon is quite complex to analyse due to the diversity of animal species, the diversity of rearing environment, the number of antimicrobial classes available and the diversity of pathogenic bacteria involved. This introductory paper includes developments on the place of antiviral compounds in veterinary medicine and a classification of antimicrobials used in food-producing animals.

Use of antimicrobial agents in livestock.

Antimicrobial agents, especially antibacterial agents, are used throughout the world, across a diverse array of extensive and intensive livestock production systems, to protect the health and welfare of livestock and to improve their performance. While some agents that are used in livestock belong to classes that have no counterpart in human medicine, this is not the case for the most widely used agents: the tetracyclines, penicillins, macrolides and sulphonamides. Many bacterial diseases of livestock cause devastating losses of animal life and productivity. As a result, their keepers can lose their livelihoods and see a dramatic reduction in income, so there is often a great sense of urgency to treat affected animals early. However, there are a large number of bacterial pathogens that cause disease and it is frequently difficult to reach a conclusive diagnosis prior to instituting treatment. There are many ways in which existing uses of antimicrobial agents can be improved, amongst the most important are increased utilisation of veterinary professional services, the introduction of enhanced infection control measures, improved point-of-care diagnostic tests, and the application of physiologically based population pharmacokinetic-pharmacodynamic modelling.

Persistent organic pollutants: potential health effects?

It is not a point of debate that the Stockholm Convention for the prevention of further accumulation of persistent organic pollutants (POPs) should be ratified and implemented by all countries. However, in their article, Schafer and Kegley present an unbalanced "worst case scenario". Approximately 20% of the food supply of the US is contaminated with POPs at extremely low levels; these levels are comparable to those found in many other countries. Furthermore, there is no scientific consensus that these levels are hazardous to most humans. More information is needed to determine the actual risks of extremely low levels of POPs to human health.

Identification of hydrolyzed inulin syrup and high-fructose corn syrup in apple juice by capillary gas chromatography: PVM 4:1999.

A peer-verified, gas chromatographic (GC) method is presented for the identification of hydrolyzed inulin syrup (HIS) and high-fructose corn syrup (HFCS) in apple juice. The procedure involves determining the Brix value of the apple juice or apple juice concentrate and preparing a dilution of the test sample to 5.5 degrees Brix. A 100 microL aliquot of the 5.5 degrees Brix test solution is then freeze-dried in a GC autosampler vial. The sugars in the freeze-dried residue are converted to trimethylsilyl derivatives, by the addition of an appropriate silylation reagent, and the vial is heated at 75 degrees C for 30 min. After derivatization, the solution is introduced into a gas chromatograph where the analytes are separated on a 30 m, 0.25 mm id DB-5 column. The method can use hydrogen, helium, or nitrogen as the carrier gas. The analytes and marker compounds are measured by use of a flame ionization detecone of the 2 syrups at 2 levels. Dilution was ascertained by the presence of retrograde sugar markers found in the 2 sugar syrups. All 3 laboratories involved in the study were able to identify the correct diluent in the blind, randomly coded, apple juice test portions. The levels of dilution in the test portions were 0, 6.9% (HIS), 16.0% (HIS), 8.1% (HFCS), and 17.0% (HFCS). No false positive results were reported. Quantitative conclusions can be drawn when the same syrup is used for dilution and as a reference standard.

The behaviour of doramectin in the gastrointestinal tract, its secretion in bile and pharmacokinetic disposition in the peripheral circulation after oral and intravenous administration to sheep.

Sheep were 'compartmentalized' by surgically implanting cannulae in the rumen, abomasum and terminal ileum with a re-entrant cannula inserted between the cystic duct and the duodenum to monitor bile secretion. Doramectin, containing a trace of [3H]-doramectin, was administered both intravenously (i.v.) and intraruminally (i.r.) at a dosage of 150 microg/kg. The pharmacokinetic behaviour of [3H]-labelled products was determined in these pools, and also in peripheral plasma, urine and faeces. Parent doramectin was also determined in plasma, abomasal digesta fluid and bile. Following i.r. administration, [3H] compounds were almost entirely associated with particulate digesta. A 14.5 h half-life in the rumen prolonged the presence of [3H] in the abomasum. Doramectin appeared to be degraded in abomasal digesta because only 24% of abomasal [3H] was attributed to the parent drug. Absorption of doramectin resulted in a systemic availability of 35%, of which 1.6 and 23.6% of the dose was contained in urine and biliary secretions, respectively. Following i.v. administration, almost negligible quantities of [3H] were secreted into the rumen or abomasum and only 2.7% of the dose was excreted in urine, whereas 132% was secreted in bile. This indicated that approximately one-third of biliary metabolites were enterohepatically recycled with biliary metabolites, elevating the proportion of [3H] in fluid digesta in the small intestine. Passage of the i.r.-administered drug through the gastrointestinal tract (GIT) resulted in virtually complete faecal excretion of [3H] within 5 days, whereas the continued secretion of i.v.-administered [3H] in bile prolonged the presence of [3H] in the GIT, with faecal clearance not being complete for at least 10 days. This multi-compartmental study has provided more information on the behaviour of doramectin than can be obtained from examining drug disposition in the peripheral circulation alone. With this knowledge, it is anticipated that opportunities for improving drug performance will be identified.

Molar absorptivities of aflatoxins B1, B2, G1, and G2 in acetonitrile, methanol, and toluene-acetonitrile (9 + 1) (modification of AOAC Official Method 971.22): collaborative study.

Four laboratories participated in a mini-collaborative study of AOAC Official Method 971.22, Standards for Aflatoxins, Thin-Layer Chromatographic Method, to extend the method to 3 replacement solvents for benzene for calibration of standard aflatoxin solutions. Triplicate test sample vials, each containing 25 micrograms of the respective aflatoxin for each of the 4 aflatoxins and for each of the solvents, were prepared and sent to each collaborator. The collaborators dissolved the aflatoxin in each vial in 2 mL solvent, measured the UV spectrum, and reported the absorptivity maxima near 350 nm. The concentrations of the aflatoxins in the test samples were determined by dissolving identical test samples in benzene-acetonitrile (98 + 2) and following the procedure described in AOAC Official Method 971.22. These concentrations were, in turn, used to determine the molar absorptivities in the other 3 solvents (see Table 1). AOAC Official Method 971.22 has been modified to extend its applicability to 3 replacement solvents for benzene for calibration of standard aflatoxin solutions.

Determination and survey of ochratoxin A in wheat, barley, and coffee--1997.

Ochratoxin A (OA) is a nephrotoxic and nephrocarcinogenic mycotoxin produced by Aspergillus and Penicillium species. It has been found mainly in cereal grains and coffee beans. The purpose of this study was to investigate the occurrence of OA in cereal grains and in coffee imported to the United States. A modified liquid chromatographic (LC) method for determining OA in green coffee was applied to wheat, barley, green coffee, and roasted coffee. The test sample was extracted with methanol-1% NaHCO3 (7 + 3), and the extract was filtered. The filtrate was diluted with phosphate-buffered saline (PBS), filtered, and passed through an immunoaffinity column. After the column was washed with PBS and then with water, OA was eluted with methanol. The eluate was evaporated to dryness, and the residue was dissolved in acetonitrile-water (1 + 1). OA was separated on a reversed-phase C18 LC column with acetonitrile-water-acetic acid (55 + 45 + 1) as eluant and quantitated with a fluorescence detector. Recoveries of OA from the 4 commodities spiked over the range 1-4 ng/g were 71-96%. The limit of detection was about 0.03 ng/g. OA contamination at > 0.03 ng/g was found in 56 of 383 wheat samples, 11 of 103 barley samples, 9 of 19 green coffee samples, and 9 of 13 roasted coffee samples. None of the coffee samples contained OA at > 5 ng/g; only 4 samples of wheat and 1 sample of barley were contaminated above this level.

Determination of deoxynivalenol in white flour, whole wheat flour, and bran by solid-phase extraction/liquid chromatography: interlaboratory study.

A liquid chromatographic (LC) method for determining deoxynivalenol (DON) in white flour, whole wheat flour, and bran at or above the U.S. Food and Drug Administration advisory level of 1 microgram/g was evaluated by an interlaboratory study. Test samples of processed wheat (flour and bran) were extracted by blending with acetonitrile-water (84 + 16). Extracts were filtered and passed through a solid-phase extraction (SPE) column. The eluate was then chromatographed on a reversed-phase LC column with a water-methanol gradient. DON was measured at 220 nm. Naturally contaminated white flour, whole wheat flour, and bran samples and spiking solutions of DON to be added to the 3 commodities at 0.5, 1.0, and 2.0 micrograms/g were sent to 4 collaborators in Kansas, Louisiana, Missouri, and Washington states. Three collaborators completed the study. Average recoveries of DON from the 3 commodities spiked at 0.5, 1.0, and 2.0 micrograms/g were 94, 87, and 97%, respectively. Within-laboratory relative standard deviations for repeatability (RSDr) ranged from 3.1 to 21.7% and between-laboratory relative standard deviations for reproducibility (RSDR) ranged from 10.8 to 38.7%. On the basis of the results of this study, the SPE/LC method for DON in white flour, whole wheat flour, and bran was adopted as a peer-verified method by AOAC INTERNATIONAL.

Effects of fumonisin B1 on lipid peroxidation in membranes.

Electron spin resonance (ESR)1 spin-label oximetry and spin trapping techniques have been used to study the effect of fumonisin B1 (FB1), an amphipathic mycotoxin on lipid peroxidation in egg yolk phosphatidylcholine (EYPC) bilayers. In the study of the interaction between FB1 and lipid bilayers our results show that fumonisin disturbs the ordering of membranes, enhances oxygen transport in membranes, and also increases membrane permeability. In our model system, lipid peroxidations were initiated by extended incubation of the liposomes, or by inducing Fe2+ ions, UV illumination of H2O2 or ultrasound irradiation. As an indication of the rates of lipid oxidation in EYPC, the consumption of molecular oxygen was studied by monitoring the oxygen concentration in the aqueous phases of the liposomes. Lipid-derived free radicals generated during the oxidation process were measured by a spin trapping method. The incorporation of FB1 in the test samples made the membranes highly susceptible to oxidation. Our results provide the first evidence that the fumonisins appear to increase the rate of oxidation, promote the free radical intermediate production and accelerate the chain reactions associated with lipid peroxidation. The disruption of membrane structure, the enlargement of the relative oxygen diffusion-concentration products, as well as the enhancement effects on membrane permeability, thus provide additional insights into potential mechanisms by which the fumonisins could enhance oxidative stress and cell damage.

Peroxidation of membrane lipids and oxidative DNA damage by fumonisin B1 in isolated rat liver nuclei.

Fumonisin B1 (FB1), a contaminant of corn, has been reported to be a hepatocarcinogen in rats. In an attempt to understand its mechanisms of action, a model system of isolated rat liver nuclei was used to determine what effects, if any, FB1 might have on nuclear membrane lipids and DNA. The data suggested that FB1 induced lipid peroxidation concurrently with DNA strand breaks in this in vitro system. Iron and copper had no statistically significant stimulatory effects on these reactions. In addition, the active oxygen scavengers catalase, superoxide dismutase (SOD), mannitol and sodium azide had no significant inhibitory effects on the FB1-induced DNA strand breaks. However, a small but significant reduction in lipid peroxidation by catalase and mannitol was observed. These results suggested that hydroxyl radicals may be the initiators of the nuclear membrane lipid peroxidation, which results in production of peroxyl radicals. In turn, the peroxyl radicals may be responsible for the DNA strand breaks. An alternative explanation is that the hydroxyl radicals, produced close to the DNA-bound metal ions, may induce direct site-specific strand breaks, which are insensitive to the scavengers of active oxygen.

Effects of fumonisin B1 and (hydrolyzed) fumonisin backbone AP1 on membranes: a spin-label study.

Electron spin resonance (ESR) spectroscopy and spin label techniques have been used to study the effects of fumonisin B1 (FB1) and hydrolyzed fumonisin backbone (AP1) on the structural and dynamic properties of phosphatidylcholine membranes at the molecular level. Multilamellar liposomes consisting of dimyristoylphosphatidylcholine (DMPC) and egg yolk phosphatidylcholine (EYPC) were used. Six different nitroxide spin labels were used to determine what effects FB1 may impart on the ordering and mobility of lipids in membranes. The experimental results disclose the following: (1) In the fluid phase membrane, FB1 significantly increases the fluidities of n-doxylstearic acid (SA) spin labels (SL) attached to carbons 5 and 7, which disorders the alkyl chains and perturbs the surface region of the bilayer; by comparison, minimal effects were detected near the center of the bilayer. (2) In the gel phase, FB1 and AP1 imparts marked rigidifying effects on membrane fluidity, which enlarges the change in ordering on the phase transition even further. (3) FB1 also restricts the mobility of the (rigid) cholestane spin label. (4) A reduction in mobility of the tempo-stearate spin label suggests that the tricarballylic acid (TCA) moieties of FB1 might mimic the structure of polar headgroups in phospholipids. The present results may provide additional mechanisms to elucidate the toxicological activities of the fumonisins.