PHENYLBUTAZONE PHARMACOKINETICS AND BIOAVAILABILITY IN THE DROMEDARY CAMEL (CAMELUS-DROMEDARIUS)

Phenylbutazone was administered intravenously and intramuscularly at a dosage rate of 4.4 mg/kg to a group of 6 female camels in a two-perio d crossover study. After intravenous (i.v.) administration, dispositio n was characterised by a two-compartment open model, with a low volume of distribution (0.174 1.kg(-1)), and distribution and elimination ha lf-lives of 0.43 and 12.51 h, respectively. After intramuscular (i.m.) dosing absorption was relatively rapid with absorption half-time and time of maximal concentration values of 1.14 and 3.95 h, respectively, Plateau concentrations of phenylbutazone in plasma were obtained betw een 2 and 12 h and mean bioavailability was 97%, although this was sub ject to wide inter-animal differences. Plasma concentrations of the ph enylbutazone metabolite, oxyphenbutazone, were low after iv dosing and generally undetectable after im administration, indicating that it is unlikely to contribute significantly to the pharmacological effects p roduced by phenylbutazone administration. An indication was obtained t hat phenylbutazone inhibited the ex vivo synthesis of serum thromboxan e B-2 (TxB(2)) for 24 h after i.v. dosing, but this finding requires c onfirmation.