Pharmacokinetics of 4-methylimidazole in sheep

The pharmacokinetics of 4-methylimidazole (4MI), a toxin found in ammoniated forage, was studied after i.v. infusion or oral administration of a single dose of 20 mg 4MI/kg BW to sheep. A two-compartment open model was used to describe i.v. infusion data. Oral data were described by a one-compartment open model. A rapid distribution phase (t1/2 alpha = 28 min) was observed after i.v. infusion. The biological half-lives obtained after i.v. infusion (t1/2 beta = 9.72 h) and oral dosing (t1/2 beta = 9.37 h) were similar. The bioavailability of oral 4MI was .69, with a relatively rapid absorption phase (t1/2abs = 1.52 h). The relatively large volume of distribution (61.6 and 65.8 liters for i.v. infusion and oral dosage, respectively) indicates that 4MI is distributed in the extravascular compartment. A dose of 20 mg/kg BW did not cause any apparent ill effects to the animals.