Pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in miniature donkeys

To describe the pharmacokinetics of phenylbutazone and oxyphenbutazone after IV administration in miniature donkeys. 6 clinically normal miniature donkeys. 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 phenylbut...

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Published inAmerican journal of veterinary research Vol. 62; no. 5; p. 673
Main Authors Matthews, N S, Peck, K E, Taylor, T S, Mealey, K L
Format Journal Article
LanguageEnglish
Published United States 01.05.2001
Subjects
Animals
Anti-Inflammatory Agents, Non-Steroidal - blood
Anti-Inflammatory Agents, Non-Steroidal - pharmacokinetics
Area Under Curve
Equidae - metabolism
Equidae - physiology
Male
Oxyphenbutazone - blood
Oxyphenbutazone - pharmacokinetics
Phenylbutazone - blood
Phenylbutazone - pharmacokinetics
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Summary:To describe the pharmacokinetics of phenylbutazone and oxyphenbutazone after IV administration in miniature donkeys. 6 clinically normal miniature donkeys. 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. 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). 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.
ISSN:0002-9645
DOI:10.2460/ajvr.2001.62.673