Pimobendan is available in the United States as a licensed oral formulation for dogs in chewable tablet form. At this time, the drug has not been labeled for use in cats.
Pimobendan (Vetmedin, bi-vetmedica.com) is an oral inodilator with a number of secondary effects. The drug exerts positive inotropic effects mainly through sensitization of the cardiac contractile apparatus to intracellular calcium. Overall, pimobendan enhances systolic function by improving the efficiency of cardiac contraction.
Pimobendan is also a phosphodiesterase (PDE)-III inhibitor, resulting in arterial and venous dilation and leading to reduction in both cardiac preload and afterload. In addition, the drug has demonstrated vasodilatory properties that are endothelium-mediated and may involve inhibition of PDE-V. This mechanism of vasodilation may be beneficial in the treatment of pulmonary hypertension (PH).
Although pimobendan is not available as an IV preparation, the oral preparation is rapidly absorbed with peak effects in 2 to 4 hours. Generic formulations have not been clinically evaluated and should be avoided. In addition, reformulation (suspensions) should be avoided since the product in solution is known to have limited stability.
In dogs, pimobendan has proven clinical efficacy for the treatment of congestive heart failure (CHF) from chronic valvular disease (CVD) or from dilated cardiomyopathy (DCM).1,2 The recommended canine dose is 0.25 to 0.3 mg/kg q12h. In later stages of heart failure or when clinical signs become refractory (stage D, Table 1), the dose frequency is increased to q8h.
In cats, there are no published studies to date on the pharmacokinetics and pharmacodynamics of pimobendan, but studies have reported off-label doses for treating feline heart failure similar to those used for dogs.3-6
Table 1. Modified ACVIM Heart Failure Classification Scheme