Pimobendan is used to treat congestive heart failure (CHF) or chronic mitral valve regurgitation (CMVI) secondary to dilated cardiomyopathy (DCM) in dogs. Myxomatous/degenerative mitral valve disease (MMVD, DMVD). Pimobendan can be used as first-line or adjunctive therapy for canine portal hypertension secondary to mitral valve disease. Its adverse reactions and contraindications are as follows.

Pharmacological Actions

Pimobendan is a potent cardiovascular dilator with both inotropic and vasodilatory effects. It has a heart rate-reducing (reducing heartbeats) effect in animals with severe chronic heart failure. It achieves its inotropic effect by inhibiting phosphodiesterase III (PDE-III) and increasing the sensitivity of intracellular calcium ions during cardiac contraction. Because pimobendan does not increase intracellular calcium ion levels, the increase in cardiac contraction is not accompanied by an increase in myocardial oxygen consumption. Pimobendan exerts its arterial and venous dilating effect by inhibiting vascular PDE-III. The vasoconstrictive effects of pimobendan are achieved by inhibiting vascular PDE-III and dilating arteries and veins. Pimobendan also has antithrombotic effects.

Adverse Reactions

In dogs, the main adverse reactions are severe gastrointestinal reactions. However, there is evidence that pimobendan may cause arrhythmias. There have been reports of atrial fibrillation or ventricular abnormalities in dogs after taking pimobendan, but since cardiomyopathy can also cause arrhythmias, it cannot be completely determined that the adverse reactions are caused by pimobendan. Experiments have shown that pimobendan can increase mortality in patients with heart failure, but this experiment has not been confirmed in dogs.

Contraindications

It is contraindicated in animals allergic to pimobendan, and is also contraindicated in animals with proliferative cardiomyopathy, aortic stenosis, or any other functional or organic reason that prevents the increase of cardiac output. Use with caution for uncontrolled arrhythmias.

Safety has not been evaluated in the following dogs: puppies less than 6 months of age, dogs with congenital heart defects, dogs with diabetes or other metabolic disorders, and female dogs used for breeding, pregnancy, or lactation.