Pharmacokinetics of sulphadiazine and trimethoprim in carp (Cyprinus carpio L.) acclimated at two different temperatures

Bioavailability and Pharmacokinetics of Sulphadiazine, N4-acetylsulphadiazine and Trimethoprim following Intravenous and Intramuscular Administration of a Sulphadiazine/Trimethoprim Combination in Sheep

The combination of sulphadiazine and trimethoprim is extensively used in farm animal species; however, there are no data concerning its pharmacokinetics after intramuscular administration in sheep. Twelve rams of the Chios breed were used to study the disposition of sulphadiazine, its metabolite N4-acetylsulphadiazine and trimethoprim after intravenous (i.v.) and intramuscular (i.m.) administration of a sulphadiazine/trimethoprim (5:1) combination in sheep. Sulphadiazine bioavailability (+/-SD) was 69.00%+/-10.51%. The half-life of the terminal phase (4.10+/-0.58 h after i. v., and 4.03+/-0.31 h after i.m. administration) was significantly higher than the respective value for trimethoprim (0.59+/-0.19 h) after i.v. administration. The maintenance of a constant plasma concentration ratio after i.v. administration was therefore impossible. The acetylation capacity in sheep, determined by the AUC ratio between N4-acetylsulphadiazine and the parent compound, sulphadiazine, was very low (less than 4%). The most remarkable finding of this study was that trimethoprim was not detected in sheep plasma after i.m. injection. In conclusion, according to the findings of the present study, following i.v. administration of the sulphadiazine/trimethoprim combination, trimethoprim can be considered as the limiting factor for any possible synergistic effect, and the i.m. route cannot be recommended in sheep.

Pharmacokinetics and oral bioavailability of sulfadiazine and trimethoprim in broiler chickens

Sulfonamides and trimethoprim are chemotherapeutics that are extensively used in various animal species. Little information about the pharmacokinetics of these compounds in chickens exists in the literature. In this study, a new commercial formulation of sulfadiazine in combination with trimethoprim was administered both intravenously and orally, according to a crossover design, to healthy, 7-week-old broilers. The plasma concentrations of the drugs were determined by validated high-performance liquid chromatographic methods, and pharmacokinetic parameters were calculated. After intravenous or oral administration of trimethoprim (6.67 mg/kg body weight) and sulfadiazine (33.34 mg/kg body weight), both active substances were rapidly eliminated from the plasma. There was a mean half-life of 1.61 h for trimethoprim and 3.2 h for sulfadiazine. The apparent volumes of distribution (2.2 and 0.43 L/kg, respectively, indicated that the tissue distribution of trimethoprim was more extensive than that of sulfadiazine. The oral bioavailability was approximately 80% for both components.

Residues of clenbuterol in tissues of the rainbow trout (Oncorhynchus mykiss)

There have been many studies on the efficacy of beta 2-adrenergic drugs as feed additives but no data are available at present on the use of clenbuterol in fish production. To evaluate the residues of clenbuterol in tissues of fish, 50 trout (Oncorhynchus mykiss) were fed for 21 days on a fish feed containing 5 ppm of the drug. The livers, muscles and skins of sample groups of fish were analysed by HPLC with visible spectrophotometric detection on days 15 and 21 of treatment and at intervals during a 30-day withdrawal time. Clenbuterol reached its highest levels in the liver (mean 440 ppb; SD = +/- 159; n = 5) on day 15 of treatment, with a slow depletion curve; 24 +/- 3 ppb was still present at the end of the withdrawal period. At this time, residues were still present in the edible tissues, i.e. muscle (5 +/- 1 ppb) and skin (7 +/- 3 ppb). Side-effects were noted during the first week of treatment.