Metronidazole pharmacokinetics in geese (Anser anser domesticus) after intravenous and oral administrations

Metronidazole (MTZ) is a 5-nitroimidazole anti-bacterial and anti-protozoal drug. In human and companion animal medicine, MTZ remains widely used due to its effectiveness against anaerobic bacteria and protozoa. In farm animals, however, MTZ is currently prohibited in several countries due to insufficient data on nitroimidazoles. The purpose of this study was to assess its pharmacokinetics (PK) in geese after single intravenous (IV) and oral (PO) administrations. Fifteen-month old healthy male geese (n = 8) were used. Geese were subjected to a two-phase, single-dose (10 mg/kg IV, 50 mg/kg PO), open, longitudinal study design with a two-week washout period between the IV and PO phases. Blood was drawn from the left wing vein to heparinized tubes at 0, 0.085 (for IV only), 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10, 24, and 48 h. Plasma MTZ concentrations were measured using HPLC coupled to an UV detector, and the data were pharmacokinetically analyzed using PKanalix™ software with a non-compartmental approach. MTZ was still quantifiable and well above the LLOQ at 24 h after both routes of administration. Following IV administration, terminal elimination half-life, volume of distribution, and total clearance were 5.47 h, 767 mL/kg, and 96 mL/h/kg, respectively. For the PO route, the bioavailability was high (85%), and the mean peak plasma concentration was 60.27 μg/mL at 1 h. When parameters were normalized for the dose, there were no statistically significant differences for any of the PK parameters between the two routes of administration. The study shows that oral administration of MTZ seems to be promising in geese, although comprehensive research on its pharmacodynamics and multiple-dose studies are necessary before its adoption in geese can be further considered.