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In this investigation the pharmacokinetics of three commonly used antibiotics, ampicillin trihydrate (10 mg/kg), gentamicin sulphate (3 mg/kg) and oxytetracycline hydrochloride (5 mg/kg), given intravenously, were each studied in five Nubian goats and five desert sheep. The pharmacokinetic parameters were described by a two-compartment open model. The results indicated that there were significant differences between the two species in some kinetic parameters of ampicillin and oxytetracycline but not gentamicin. Ampicillin elimination half life (t[1/2beta]) in goats (1.20 h) was shorter than that in sheep (2.48 h), and its clearance (Cl) significantly higher in goats (2921 mL/h x kg) compared to sheep (262 mL/h x kg) (P < 0.01). Ampicillin volume of distribution (Vd[area]) was found to be significantly larger in goats (5673 mL/kg) than in sheep (992 mL/kg) (P < 0.01). For oxytetracycline, the t(1/2beta) in goats (3.89 h) was significantly shorter than that in sheep (6.30 h) and the Cl value in goats (437 mL/h x kg) was significantly higher than in sheep (281 mL/h x kg). The results suggest that when treating sheep and goats, the pharmacokinetic differences between the two species must be considered in order to optimize the therapeutic doses of ampicillin and oxytetracycline.

The pharmacokinetics of antipyrine and sulphadimidine were studied in male camels, sheep and goats. The two drugs were administered concomitantly. Following intravenous injection of antipyrine (25 mg/kg) and sulphadimidine (sulfamethazine) (100 mg/kg), the pharmacokinetics of the two drugs were adequately described by a one-compartment model. Antipyrine half-life in goats (2.58 h) was shorter than that in sheep (4.04 h) and camels (18.78 h). The plasma clearance was greatest in goats then sheep and then camels. For sulphadimidine, a significantly greater volume of distribution was observed in camels and the greatest plasma clearance and shortest half-life were reported in goats. Sulphadimidine half-life was 2.77 h in goats, 4.72 h in sheep and 7.36 h in camels. The present results suggest that goats have the fastest elimination of these drugs from the circulation, followed by sheep and then camels.

The pharmacokinetics of amoxicillin were studied in five Desert sheep and five Nubian goats after intravenous (i.v.) or intramuscular (i.m.) administration of a single dose of 10 mg/kg body weight. Following i.v. injection, the plasma concentration-versus-time data were best described by a two-compartment open model. The kinetic variables were similar in both species except for the volume of the central compartment (Vc), which was larger in sheep (p<0.05). Following i.m. injection, except for the longer half-life time of absorption in goats (p<0.05), there were no significant differences in other pharmacokinetic parameters between sheep and goats. The route of amoxicillin administration had no significant effect on the terminal elimination half-life in either species. The bioavailability of the drug (F) after i.m. administration was high (> 0.90) in both species. These results indicate that the pharmacokinetics of amoxicillin did not differ between sheep and goats; furthermore, because of the high availability and short half-life of absorption, the i.m. route gives similar results to the i.v. route. Therefore, identical intramuscular and intravenous dose regimens should be applicable to both species.