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Abstract

Objective—To determine the disposition of a bolus of meloxicam (administered IV) in horses and donkeys (Equus asinus) and compare the relative pharmacokinetic variables between the species.

Animals—5 clinically normal horses and 5 clinically normal donkeys.

Procedures—Blood samples were collected before and after IV administration of a bolus of meloxicam (0.6 mg/kg). Serum meloxicam concentrations were determined in triplicate via high-performance liquid chromatography. The serum concentration-time curve for each horse and donkey was analyzed separately to estimate standard noncompartmental pharmacokinetic variables.

Results—In horses and donkeys, mean ± SD area under the curve was 18.8 ± 7.31 μg/mL/h and 4.6 ± 2.55 μg/mL/h, respectively; mean residence time (MRT) was 9.6 ± 9.24 hours and 0.6 ± 0.36 hours, respectively. Total body clearance (CLT) was 34.7 ± 9.21 mL/kg/h in horses and 187.9 ± 147.26 mL/kg/h in donkeys. Volume of distribution at steady state (VDSS) was 270 ± 160.5 mL/kg in horses and 93.2 ± 33.74 mL/kg in donkeys. All values, except VDSS, were significantly different between donkeys and horses.

Conclusions and Clinical Relevance—The small VDSS of meloxicam in horses and donkeys (attributed to high protein binding) was similar to values determined for other nonsteroidal anti-inflammatory drugs. Compared with other species, horses had a much shorter MRT and greater CLT for meloxicam, indicating a rapid elimination of the drug from plasma; the even shorter MRT and greater CLT of meloxicam in donkeys, compared with horses, may make the use of the drug in this species impractical.

Full access
in American Journal of Veterinary Research

SUMMARY

Sixteen horses were allotted to 4 groups of 4 horses each to evaluate the effect of tendon sheath lavage with 4 solutions (balanced electrolyte solution, 0.1% povidone-iodine, 0.5% povidone-iodine, and 0.5% chlorhexidine). The synovitis caused by 0.1% povidone-iodine lavage was not appreciably worse than that caused by balanced electrolyte solution lavage, but the 0.5% povidone-iodine and chlorhexidine lavages caused severe synovitis, and, therefore, should not be used for tendon sheath lavage.

Free access
in American Journal of Veterinary Research

Summary

Six Jersey cows were implanted with 8 pairs of bipolar electrodes: 1 in the jejunum, 1 in the ileum, 3 in the cecum, and 3 in the proximal loop of the ascending colon (plac). Myoelectric activity was recorded at 2- to 3-day intervals, 3 times for 8 hours or 4 times for 6 hours, using a computer-based oscillograph and data-acquisition program.

Mean (± sd) duration of the migrating myoelectric complex (mmc) in the ileum was 84.52 ± 4.87 minutes. Phases I and II of the mmc lasted significantly (P < 0.05) longer than phase III. Two types (A and B) of cyclic activity were found in the cecum and plac. Cyclic activity type A was observed predominantly in the cecum, and type B was observed exclusively in the plac. Phase III of the mmc in the ileum was accompanied by hyperactivity type A at the level of the ileocecocolic junction in 60.90 ± 12.65% of the mmc. Twenty-seven types of orally and aborally propagated spike sequences, involving the cecum and plac, were found. They were most frequent when an mmc phase III was observed in the ileum, and least frequent when an mmc phase I was observed in the ileum (P < 0.05). All electrode sites of the cecum and plac served as pacemaker areas. Propagated and nonpropagated spikes were found at all electrode sites of the cecum and plac. Although propagated spikes lasted significantly (P < 0.05) longer than nonpropagated spikes, a clear distinction on the basis of duration could not be defined between the 2 spike types because broad overlapping of duration existed. Duration of cecocolic spiking activity per electrode (expressed as percentage of time) was significantly (P < 0.05) greater during mmc phase III in the ileum than during mmc phase I.

It can be concluded that myoelectric activity of the cecum is well coordinated with the ileum and the plac. Phases of reduced and increased myoelectric activity in the cecum and plac are simultaneous with phases I and III of the mmc in the ileum.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare serum disposition of flunixin meglumine after IV administration of a bolus to horses, donkeys, and mules.

Animals

3 clinically normal horses, 5 clinically normal donkeys, and 5 clinically normal mules.

Procedure

Blood samples were collected at time zero (before) and 5, 10, 15, 30, and 45 minutes, and at 1, 1.25, 1.5, 1.75, 2, 2.5, 2.75, 3, 3.5, 4, 4.5, 5, 5.5, 6, and 8 hours after IV administration of a bolus of flunixin meglumine (1.1 mg/kg of body weight). Serum was analyzed in duplicate by the use of high-performance liquid chromatography for determination of flunixin meglumine concentrations. The serum concentration-time curve for each horse, donkey, and mule were analyzed separately to estimate noncompartmental pharmacokinetic variables

Results

Mean (± SD) area under the curve for donkeys (646 ± 148 minute • µg/ml) was significantly less than for horses (976 ± 168 minute • μg/ml) or for mules (860 ± 343 minute • µg/ml). Mean residence time for donkeys (54.6 ± 7 minutes) was significantly less than for horses (110 ± 24 minutes) or for mules (93 ± 30 minutes). Mean total body clearance for donkeys (1.78 ± 0.5 ml/kg/h) was significantly different from that for horses (1.14 ± 0.18 ml/kg/h) but not from that for mules (1.4 ± 0.5 ml/kg/h). Significant differences were not found between horses and mules for any pharmacokinetic variable.

Conclusion and Clinical Relevance

Significant differences exist with regard to serum disposition of flunixin meglumine in donkeys, compared with that for horses and mules. Consequently, flunixin meglumine dosing regimens used in horses may be inappropriate for use in donkeys. (Am J Vet Res 1999;60:1441–1444)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To describe the pharmacokinetics of phenylbutazone and oxyphenbutazone after IV administration in miniature donkeys.

Animals—6 clinically normal miniature donkeys.

Procedure—Blood samples were collected before and 5, 10, 20, 30, 45, 60, 90, 120, 180, 240, 300, 360, and 480 minutes after IV administration of phenylbutazone (4.4 mg/kg of body weight). Serum was analyzed in triplicate by use of high-performance liquid chromatography for determination of phenylbutazone and oxyphenbutazone concentrations. The serum concentration-time curve for each donkey was analyzed separately to estimate model-independent pharmacokinetic variables.

Results—Serum concentrations decreased rapidly after IV administration of phenylbutazone, and they reached undetectable concentrations within 4 hours. Values for mean residence time ranged from 0.5 to 3.0 hours (median, 1.1 hour), whereas total body clearance ranged from 4.2 to 7.5 ml/kg/ min (mean, 5.8 ml/kg/ min). Oxyphenbutazone appeared rapidly in the serum; time to peak concentration ranged from 13 to 41 minutes (mean, 26.4 minutes), and peak concentration in serum ranged from 2.8 to 4.0 mg/ml (mean, 3.5 μg/ml).

Conclusion and Clinical Relevance—Clearance of phenylbutazone in miniature donkeys after injection of a single dose (4.4 mg/kg, IV) is rapid. Compared with horses, miniature donkeys may require more frequent administration of phenylbutazone to achieve therapeutic efficacy. (Am J Vet Res 2001;62:673–675)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare plasma disposition of the R(–) and S(+) enantiomers of carprofen after IV administration of a bolus dose to donkeys and horses.

Animals—5 clinically normal donkeys and 3 clinically normal horses.

Procedure—Blood samples were collected from all animals at time 0 (before) and at 10, 15, 20, 30, and 45 minutes and 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 10, 24, 28, 32, and 48 hours after IV administration of a bolus of carprofen (0.7 mg/kg). Plasma was analyzed in triplicate via high-performance liquid chromatography to determine the concentrations of the carprofen enantiomers. A plasma concentration-time curve for each donkey and horse was analyzed separately to estimate noncompartmental pharmacokinetic variables.

Results—In donkeys and horses, the area under the plasma concentration versus time curve (AUC) was greater for the R(–) carprofen enantiomer than it was for the S(+) carprofen enantiomer. For the R(–) carprofen enantiomer, the AUC and mean residence time (MRT) were significantly less and total body clearance (ClT) was significantly greater in horses, compared with donkeys. For the S(+) carprofen enantiomer, AUC and MRT were significantly less and ClT and apparent volume of distribution at steady state were significantly greater in horses, compared with donkeys.

Conclusions and Clinical Relevance—Results have suggested that the dosing intervals for carprofen that are used in horses may not be appropriate for use in donkeys. (Am J Vet Res 2004;65:1479–1482)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare serum disposition of sulfamethoxazole and trimethoprim after IV administration to donkeys, mules, and horses.

Animals—5 donkeys, 5 mules, and 3 horses.

Procedure—Blood samples were collected before (time 0) and 5, 15, 30, and 45 minutes and 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 8, 10, and 24 hours after IV administration of sulfamethoxazole (12.5 mg/kg) and trimethoprim (2.5 mg/kg). Serum was analyzed in triplicate with high-performance liquid chromatography for determination of sulfamethoxazole and trimethoprim concentrations. Serum concentration-time curve for each animal was analyzed separately to estimate noncompartmental pharmacokinetic variables.

Results—Clearance of trimethoprim and sulfamethoxazole in donkeys was significantly faster than in mules or horses. In donkeys, mean residence time (MRT) of sulfamethoxazole (2.5 hours) was less than half the MRT in mules (6.2 hours); MRT of trimethoprim in donkeys (0.8 hours) was half that in horses (1.5 hours). Volume of distribution at steady state (Vdss) for sulfamethoxazole did not differ, but Vdss of trimethoprim was significantly greater in horses than mules or donkeys. Area under the curve for sulfamethoxazole and trimethoprim was higher in mules than in horses or donkeys.

Conclusions and Clinical Relevance—Dosing intervals for IV administration of trimethoprim-sulfamethoxazole in horses may not be appropriate for use in donkeys or mules. Donkeys eliminate the drugs rapidly, compared with horses. Ratios of trimethoprim and sulfamethoxazole optimum for antibacterial activity are maintained for only a short duration in horses, donkeys, and mules. (Am J Vet Res 2002;63:349–353)

Full access
in American Journal of Veterinary Research

Summary

Cortical bone screws were implanted into the proximal portion of the right and left radius and ulna of 6 newborn Quarter Horse foals as radiographic markers for measurement of growth. Distance between markers on a lateral radiographic view was measured. Radiographs were taken at 2-week intervals until the horses were 8 weeks old, at 4-week intervals until they were 48 weeks old, and at 12-week intervals until they were 72 weeks old.

The proximal radius and ulna grew at similar rates during the 72-week period of evaluation, and growth continued throughout 72 weeks. The proximal radius grew 3.5 cm, and the ulna grew 3.4 cm. Although the rates of growth were similar, growth from the ulnar physis contributed only to the length of the olecranon; growth was not transmitted to the ulnar diaphysis distal to the cubital joint. The proximal radius slid distally in relation to the ulna as growth occurred at the proximal radial physis.

These findings suggest that transfixing the ulna to the radius while growth is occurring at the proximal radial physis impedes the natural shifting process, and subluxation of the elbow can result. Severity of subluxation would be inversely related to the age of the horse at the time of transfixation.

Free access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Summary

Postoperative performance and behavioral patterns were investigated retrospectively in 23 client-owned mares after bilateral ovariectomy via colpotomy. The interval from surgery to postoperative inquiries ranged from 9 to 67 months. Information obtained from review of the medical record and client interviews included the reason for ovariectomy, postoperative complications, problems identified by owners after discharge of the mare from the hospital, postoperative level of athletic performance, postoperative signs of estrus, and overall owner satisfaction. Reasons given by owners for having mares ovariectomized were behavioral modification (16 mares), use as embryo-transfer recipients (3 mares), use as mount mares for collecting semen (2 mares), elimination of chronic colic during estrus (1 mare), and sterilization for registration (1 mare). Postoperative complications developed in 4% (1/23) of the mares; however, problems were noticed by the owners of 4 other mares after discharge from the hospital. Continuing signs of behavioral estrus were detected in 35% (8/23) of the mares, but in only in 9% (2/23) was the behavior judged to be objectionable by the owner. Of 12 mares used in performance events prior to bilateral ovariectomy, 10 were judged to be competing at greater than preoperative levels, 1 was judged to be competing at the same level, and 1 was judged to be competing at less than preoperative level of performance. Of 18 owners, 14 were satisfied, 2 were undecided, and 2 were dissatisfied with their mare after it had had bilateral ovariectomy.

Free access
in Journal of the American Veterinary Medical Association