Absorption, tissue distribution, metabolism and excretion of ormetoprim and sulphadimethoxine in Atlantic salmon (Salmo salar) after intravenous and oral administration of Romet³⁰

Abstract

1. Uptake, bioavailability, tissue disposition and elimination of sulphadimethoxine (SDM) and ormetoprim (OMP) were examined in Atlantic salmon (Salmo salar) following intravenous and oral administration of Romet³⁰ at a dose of 5 mg OMP and 25 mg SDM kg_-1 fish.

2. Plasma clearance was rapid for both drugs following a single i.v. dose, characterized by t_1/2α = 0.48 and 0.54h, t_1/2β = 9.9 and 25.6h for SDM and OMP respectively with a volume of distribution (Vss) = 0.389 and 2.4781kg^-1.

3. Following oral administration, peak plasma concentrations of 1.13 and 9.99μgml^-1 were achieved after 17.6 and 20.3h for OMP and SDM respectively. Bioavailabilities were 85% for OMP and 39% for SDM.

4. Oral administration revealed the highest concentration of OMP in kidney and liver whereas the highest concentrations of SDM were found in muscle and bile.

5. High concentrations of N⁴-acetylated SDM were found in the bile indicating significant metabolism of SDM.