Pharmacodynamic properties
Pimobendan, a benzimidazole-pyridazinone derivative, is a non-sympathomimetic, non-glycoside inotropic substance with potent vasodilatative properties. Pimobendan exerts its stimulatory myocardial effect by a dual mechanism of action: increase in calcium sensitivity of cardiac myofilaments and inhibition of phosphodiesterase (type III). It also exhibits a vasodilating action through an inhibitory action on phosphodiesterase III activity.
Pharmacokinetic properties
Absorption: Due to the intravenous administration, the bioavailability is 100 %.
Distribution: After intravenous administration the volume of distribution is 2.6 l/kg indicating that pimobendan is distributed readily into the tissues. The mean plasma protein binding is 93 %.
Metabolism: The compound is oxidatively demethylated to its major active metabolite (UD-CG 212). Further metabolic pathways are phase II conjugates of UD-CG 212, in essence glucuronides and sulfates.
Elimination: Following intravenous administration, the plasma elimination half-life of pimobendan is 0.4 + 0.1 hours, consistent with the high clearance of 90 + 19 ml/min/kg and a short mean residence time of 0.5 + 0.1 hours. The main active metabolite is eliminated with plasma elimination half-life of 2.0 ± 0.3 hours. Almost the entire dose is eliminated via faeces.