The pharmacokinetic determinants of doxycycline were calculated after a single IV administration of the drug (20 mg/kg of body weight) in 5 Angus calves with mature rumen function and 4 Holstein calves with immature rumen function. Doxycycline disposition was best described by means of an open 2-compartment model. Median elimination half-life was 14.17 hours (Angus) and 9.84 hours (Holstein). Mean (+/- SEM total body clearance was 1.07 (+/- 0.06) and 2.20 (+/- 0.21) ml/min/kg in Angus and Holstein calves, respectively. Mean extent of doxycycline binding to serum proteins was 92.3% (+/- 0.8%). The large steady-state volume of distribution (1.31 +/- 0.11 L/kg in Angus and 1.81 +/- 0.24 L/kg in Holstein calves), despite the small free fraction in serum, suggested a relatively unrestricted access of drug into the intracellular compartment and/or appreciable tissue binding. Results of mass spectrometric analysis of serum and urine from calves administered doxycycline IV revealed absence of biotransformation, because only parent drug could be detected. Thus, doxycycline may be a valuable antibiotic for use in food animals pending further studies on tissue residues, safety, and efficacy.

The detection of volatile fatty acids (VFA) by gas chromatography of 85 purulent specimens from abscesses or pyogenic infections in cats, dogs, rodents, and ruminants was compared with the results of bacteriologic culturing, and proved to be a rapid means of presumptively diagnosing anaerobic infections. Of 83 bacteriologically positive specimens, 52 (61%) yielded obligate anaerobes and in 50 specimens, 1 or more VFA (butyric acid, isobutyric acid, valeric acid, isovaleric acid, caproic acid, or isocaproic acid) was detected. Forty-six specimens were positive for culturing of anaerobes and for detection of 1 or more of these VFA. By contrast, pus from infections caused by (facultative) aerobic microorganisms contained no VFA or only acetic and/or propionic acid.

In addition to its well-known physicochemical properties, hyaluronate (HA) has recently been shown to have important biological and pathophysiologic regulatory effects on granulocytes, monocytes, fibroblasts, and endothelial cells, as well as on the healing of wounds and various joint disorders. Many of these effects depend on or are reflected in the concentration and degree of polymerization of HA. Therefore, high-performance liquid chromatography with size-exclusion column was used to characterize the concentration and degree of polymerization of HA in equine synovial fluid (SF). The mean (+/-SD) HA concentration was 0.47 +/- 0.19 mg/ml and there was no difference between control joints and those with positive response to local anesthetic administration (0.61 +/- 0.20 mg/ml vs 0.42 +/-0.17 mg/ml), suggesting that in horses with acute traumatic synovitis causing lameness, HA concentration in SF cannot be used as a marker for the condition. High-performance liquid chromatograms disclosed considerable variation between horses in the degree of polymerization reflected in the peak area to height ratio (mean +/-SD, 3.207 +/- 0.447; range, 2.229 to 3.915), indicating differences in local synthesis, degradation, or mobilization into lymph of SF HA. In addition, the correlation between SF HA concentration and degree of polymerization was 0.760 (P < 0.01; linear regression analysis) suggesting that HA concentration and chain length are independently regulated.

Objective: To evaluate 4 methods used to measure plasma insulin-like growth factor (IGF) 1 concentrations in healthy cats and cats with diabetes mellitus or other diseases. Animals: 39 healthy cats, 7 cats with diabetes mellitus, and 33 cats with other diseases. Procedures: 4 assays preceded by different sample preparation methods were evaluated, including acid chromatography followed by radioimmunoassay (AC-RIA), acid-ethanol extraction followed by immunoradiometry assay (AEE-IRMA), acidification followed by immunochemiluminescence assay (A-ICMA), and IGF-2 excess followed by RIA (IE-RIA). Validation of the methods included determination of precision, accuracy, and recovery. The concentration of IGF-1 was measured with all methods, and results were compared among cat groups. Results: The intra-assay coefficient of variation was < 10% for AC-RIA, A-ICMA, and AEE-IRMA and 14% to 22% for IE-RIA. The linearity of dilution was close to 1 for each method. Recovery rates ranged from 69% to 119%. Five healthy cats had IGF-1 concentrations > 1,000 ng/mLwith the AEE-IRMA, but < 1,000 ng/mL with the other methods. Compared with healthy cats, hyperthyroid cats had significantly higher concentrations of IGF-1 with the A-ICMA method, but lower concentrations with the IE-RIA method. Cats with lymphoma had lower IGF-1 concentrations than did healthy cats regardless of the method used. Conclusions and Clinical Relevance: Differences in the methodologies of assays for IGF-1 may explain, at least in part, the conflicting results previously reported in diabetic cats. Disorders such as hyperthyroidism and lymphoma affected IGF-1 concentrations, making interpretation of results more difficult if these conditions are present in cats with diabetes mellitus.

Objective-To determine the pharmacokinetic disposition of IV administered caffeine in healthy Lama spp camelids. Animals-4 adult male alpacas and 4 adult female llamas. Procedures-Caffeine (3 mg/kg) was administered as an IV bolus. Plasma caffeine concentrations were determined by use of high-performance liquid chromatography in 6 animals and by use of liquid chromatography-mass spectrometry in 2 llamas. Results-Median elimination half-life was 11 hours (range, 9.3 to 29.8 hours) in alpacas and 16 hours (range, 5.4 to 17 hours) in llamas. The volume of distribution at steady state was 0.60 L/kg (range, 0.45 to 0.93 L/kg) in alpacas and 0.75 L/kg (range, 0.68 to 1.15 L/kg) in llamas. Total plasma clearance was 44 mL/h/kg (range, 24 to 56 mL/h/kg) in alpacas and 42 mL/h/kg (range, 30 to 109 mL/h/kg) in llamas. Conclusions and Clinical Relevance-High-performance liquid chromatography and liquid chromatography-mass spectrometry were suitable methods for determination of plasma caffeine concentrations in alpacas and llamas. Plasma caffeine concentration-time curves were best described by a 2-compartment model. Elimination half-lives, plasma clearance, volume of distribution at steady state, and mean residence time were not significantly different between alpacas and llamas. Intravenous administration of caffeine at a dose of 3 mg/kg did not induce clinical signs of excitement.

This study was conducted to evaluate the ELISA kit for measuring the level of cortisol in the urine. The CV of within-run variation and day to day variation were 0.4-2.8 and 1.8-5.7, respectively. the minimum limitation of measurement was 1ng/ml. the cross reaction was high (CR50(%)=11.4-43.2) in prednisolone, 11-deoxycortisol, 21-deoxycortisol and predinosone. There was low and no cross reaction in other steroid. To develop the ELISA kit we measured the cortisol level in diluted urine with PBS (procedure I), extracted urine with methylene chloride (procedure II) and extracted methylene chloride-extracted urine from thin-layer chromatography (procedure III). The CV value of procedure I, II, III was 9.4-28.3%, 7.2-8.9% and 2.5-5.7%, respectively. There was significant difference between procedure I with II, and pro-cedure I with III(p0.01), but no difference between procedure II with III significantly(p0.01). The mean UCCR of urine collected through am 8 to 10 ws 9.5+_7.6(0.14-28.0) in 12-month-old dog(n

Naproxen (+ 6-methoxy-[alpha - methyl]- 2-naphthalene acetic acid) is a nonsteroidal anti-inflammatory drug that is used for the treatment of inflammatory conditions in horses. We developed a model that describes the drug's disposition and renal excretion, including synovial fluid disposition and elimination after IV administration in horses. The plasma disposition, after IV administration of 5 mg/kg of body weight, was described by a two-compartment model; mean +/- SD distribution and elimination half-lives were 1.42 +/- 0.42 and 8.26 +/- 2.56 hours, respectively. Plasma concentration of naproxen after IV administration of 5 mg/kg was 55.3 +/- 13.5 and 0.61 +/- 0.42 mg/L at 5 minutes and 48 hours after its administration, respectively. Steady-state volume of distribution was 0.163 +/- 0.053 L/kg, and area under the plasma concentration time-curve was 372.1 +/- 128.2 mg/h/L The peak synovial fluid concentration of 12.68 +/- 12.39 mg/L was measured at 6 hours, and decreased to 0.71 +/- 0.38 mg/L at 36 hours after naproxen administration. The decrease of naproxen concentration in synovial fluid paralleled that in plasma. The appearance half-life of naproxen in synovial fluid was 4.64 hours, and the elimination half-life was 6.73 hours. Total body clearance was 0.015 +/- 0.006 L/h/ kg. The percentage of plasma protein binding was 97.0 +/- 2.9% at plasma concentrations between 5 and 100 mg/L. This was significantly (P < 0.05) higher than the percentage of binding at plasma concentrations of 0.5, 1, and 500 mg/L, which was 75.2 +/- 11.8%. Most of the drug was excreted as glucuronidated naproxen and unconjugated desmethylnaproxen. The recovery of naproxen and all metabolites in urine at 36 hours was 64.6 +/- 7.2% of the total dose. Of this total, 39.6 +/- 10.3% and 8.5 +/- 7.9% were glucuronidated naporoxen and desmethylnaproxen, respectively; 0.3 +/- 0.1% and 16.6 +/- 7.9% were free naproxen and desmethylnaproxen, respectively.

Using 7 penicillins (amoxicillin, ampicillin, methicillin, penicillin G, oxacillin, cloxacillin, and dicloxacillin), simultaneous and direct determination of residual penicillins in biological samples was carried out by use of bioassay and high-performance liquid chromatography with spectrophotometric or fluorometric detectors. By use of assay medium seeded with penicillin-sensitive Micrococcus luteus (ATCC No. 9341) as a test organism, we were able to detect penicillins even at low concentrations. All penicillins treated with 10 U of penicillinase/ml did not produce inhibition zones by disk testing, even at a concentration of 100 micrograms of penicillin/ml/assay plate. Using a mobile phase of acetonitrile:methanol:0.01M KH2PO4 (19:11:70, v/v/v; pH, 7.1), standard solutions of the penicillins were separated from each other by use of high-performance liquid chromatography analysis, producing symmetric peaks without tailing, each of which had a characteristic retention time. Simultaneous detection of residual penicillins in bovine serum, kidneys, and liver, for the 5 penicillins for which analysis was possible by use of the UV method, yielded recovery rates from 71.4 to 102.3%; for the 2 amino-penicillins, amoxicillin and ampicillin, which could only be detected by use of the fluorometric method, recovery rate ranged from 72.9 to 103%.

A radioimmunoassay test for tetracyclines (Charm II) was compared with high-pressure liquid chromatography (HPLC) for detection of oxytetracycline (OTC) residues in milk samples from individual lactating cows. Oxytetracycline was administered by 1 of 3 routes (IV, IM, or intrauterine) to 21 lactating dairy cows. A total of 292 duplicate milk samples were collected from milkings before and through 156 hours after OTC administration. Concentration of OTC in these samples was determined by use of the Charm II test and an HPLC method with a lower limit of quantitation, approximately 2 ng of OTC/ml. Samples were also classified with respect to presence of OTC residues relative to the FDA safe concentration (less than or equal to 30 ng/ml), using the Charm II (by control point determination) and HPLC methods. There was a significant (P less than or equal to 0.05) difference between test methods in classification of milk samples with respect to presence or absence of OTC at the FDA safe concentration. A total of 48 of the 292 test results (16.4%) did not agree. Using the HPLC test results as the standard with which Charm II test results were compared, 47 false presumptive-violative test results and 1 false presumptive-nonviolative Charm II test result (a sample containing 31 ng of OTC/ml, as evaluated by HPLC) were obtained. The samples with false presumptive-violative Charm II results contained (less than or equal to 30 ng of OTC/ml, as evaluated by HPLC. In some respects, the Charm II test performed appropriately as a screening test to detect OTC residues in milk samples from individual cows. However, the tendency for the test to yield presumptive-violative test results at OTC concentrations lower than the FDA safe concentration (as evaluated by HPLC), suggests that caution should be exercised in using the test as the sole basis on which a decision is made to reject milk. As indicated by the manufacturer, presumptive-violative Charm II test results should be confirmed by additional testing Although not specifically evaluated, the tendency for misclassification of milk samples as presumptive-violative by the Charm II test may or may not occur in commingled milk, compared with milk samples from individual cows.

A cross-over study was performed in 6 healthy mixed-breed dogs and 4 healthy Beagles. Diazepam was administered per rectum to Beagles (0.5 mg/kg of body weight) and mixed-breed dogs (2 mg/kg), and IV (0.5 mg/kg) to both groups of dogs. Each dog received the drug by both routes, with a 1-week washout period between dosages. After diazepam administration, blood samples were collected to measure plasma concentration of diazepam and its active metabolites, desmethyldiazepam and oxazepam, by use of reverse-phase high-performance liquid chromatography (HPLC). Systemic availability was assessed by comparing the area under the curve for diazepam metabolites for each route of administration. Mean (+/- SD) diazepam concentrations in plasma after rectal administration were low in comparison with those obtained after IV administration, with systemic availability of only 7.4 (+/- 5.9) and 2.7 (+/- 3.2)% for the high and low dose, respectively. However, diazepam was converted to its metabolites within minutes after administration. Accounting for the total concentration of benzodiazepines (diazepam plus desmethyldiazepam and oxazepam) in plasma, systemic availability was 79.9 (+/- 20.7) and 66.0 (+/- 23.8)% for the high and low dosage, respectively. After IV administration, diazepam concentration decreased, with a half-life of only 14 to 16 minutes, but desmethyldiazepam and oxazepam concentrations decreased more slowly, with a half-life of 2.2 to 2.8 hours and 3.5 to 5.1 hours, respectively. Each of the metabolites is reported to have anticonvulsant activity. After rectal administration of the high dose, mean total benzodiazepine concentration was above 1.0 micrograms/ml within 10 minutes and was maintained above this concentration for at least 6 hours. We conclude that diazepam is absorbed after rectal administration in dogs, and that the pharmacologic effects are probably caused by the active metabolites, not the parent drug. Samples also were analyzed by use of a nonspecific commercial benzodiazepine fluorescence polarization immunoassay (FPIA). Correlation between the FPLA and HPLC assay was strongest for diazeparn (R2 = 0.84), weak for desmethyldiazepam (R2 = 0.09), and nonexistent for oxazepam. We conclude from a comparison of assays that HPLC is preferred over the FPLA method for measuring benzodiazepines in dogs.