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Am J Vet Res. 2001 May;62(5):673-5.

Pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in miniature donkeys.

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1
Texas Veterinary Medical Center, Texas A&M University, College Station 77843, USA.

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 microg/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.

PMID:
11341383
[Indexed for MEDLINE]
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