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The pharmacokinetics of doxycycline were investigated in sheep after oral (PO) and intravenous (IV) administration. The IV data were best described using a 2-(n = 5) or 3-(n = 6) compartmental open model. Mean pharmacokinetic parameters obtained using a 2-compartmental model included a volume of distribution at steady-state (V ss ) of 1.759 ± 0.3149 L/kg, a total clearance (Cl) of 3.045 ± 0.5264 mL/ kg/min and an elimination half-life (t 1/2b ) of 7.027 ± 1.128 h. Comparative values obtained from the 3-compartmental mean values were: V ss of 1.801 ± 0.3429 L/kg, a Cl of 2.634 ± 0.6376 mL/kg/min and a t 1/2b of 12.11 ± 2.060 h. Mean residence time (MRT 0À1 ) was 11.18 ± 3.152 h. After PO administration, the data were best described by a 2-compartment open model. The pharmacokinetic parameter mean values were: maximum plasma concentration (C max ), 2.130 ± 0.950 lg/mL; time to reach C max (t max ), 3.595 ± 3.348 h, and absorption half-life (t 1=2k 01 ), 36.28 ± 14.57 h. Non-compartmental parameter values were: C max , 2.182 ± 0.9117 lg/mL; t max , 3.432 ± 3.307 h; F, 35.77 ± 10.20%, and mean absorption time (MAT 0-1 ), 25.55 ± 15.27 h. These results suggest that PO administration of doxycycline could be useful as an antimicrobial drug in sheep.

Enrofloxacin is a fluorquinolone exclusively developed for use in veterinary medicine (1980). The kinetics of enrofloxacin are characterized, in general terms, by high bioavailability in most species and rapid absorption after IM, SC or oral administration. However, several studies reported that enrofloxacin showed low bioavailability after oral administration in ruminants. This drug has a broad distribution in the organism, excellent tissue penetration and long serum half-life. Also, enrofloxacin is characterized by a low host toxicity, a broad antibacterial spectrum and high bactericidal activity against major pathogenic bacteria (both Gram-positive and Gram-negative), and intracellular organisms found in diseased animals. The kinetics vary according to the route of administration, formulation, animal species, age, body condition, and physiological status, all of which contribute to differences in drug efficacy. The pharmacokinetic properties of drugs are closely related to their pharmacological efficiency, so it is important to know their behavior in each species that is used. This article reviews the pharmacokinetics of enrofloxacin in several domestic animal species.

Dietary fibers are widely used in hypoglycaemic, hypolipidemic, slimming diets. It is probable that their ingestion coincides with the oral administration of drugs and a modification of their pharmacokinetics can appear. In the present study, the influence of two soluble fibers (guar gum and psyllium) was evaluated on the pharmacokinetics of ethinyloestradiol (EE) when they were administered together to female rabbits via the oral route. Three groups of rabbits were used. All animals received 1 mg/kg of EE; this compound was administered alone in the control group and with 3.5 g of guar gum or psyllium in the other two groups. When guar gum was administered, there was a decrease in the extent of EE absorbed, but no change was observed in the rate of absorption. When psyllium was administered, the extent of EE absorbed increased slightly and the rate of absorption was slower.