Description

Pimobendan is a new inotropic agent with vasodilator properties. This heart medication is used to treat dogs with congestive heart failure (CHF), usually caused by either dilated cardiomyopathy or valvular insufficiency. Its use in cats to treat heart failure is 'off label' or 'extra label'.

Uses

Pimobendan, a combined positive inotrope (calcium sensitizer) and vasodilator (phosphodiesterase-III inhibitor) has become the standard of care for dogs with advanced heart disease. This drug confers survival benefits in dogs with congestive heart failure (CHF) secondary to dilated cardiomyopathy (DCM) and degenerative mitral valve disease (DMVD), as well as benefit in delaying the onset of CHF in dogs with preclinical DCM and advanced preclinical DMVD[1].

No consensus exists about the off-label use of pimobendan in cats with CHF. The most common cause of CHF in cats is hypertrophic cardiomyopathy (HCM), a disease of primarily diastolic dysfunction for which positive inotrope treatment might appear counterintuitive. In cats with hypertrophic obstructive cardiomyopathy (HOCM), pimobendan could be contraindicated because increased contractility could worsen the degree of dynamic left ventricular (LV) outflow tract obstruction (OTO)[2]. However, biventricular longitudinal systolic dysfunction is a feature of HCM in cats, suggesting that positive inotropy could confer therapeutic benefits. Other potential ancillary benefits of using pimobendan in cats with HCM include positive lusitropy, improved left atrial (LA) function, balanced vasodilation, increased renal blood flow, and adjunctive anti-cytokine and antiplatelet effects.

Side effects

The most common side effects include gastrointestinal effects such as decreased appetite and diarrhea. Other possible side effects include lethargy and difficulty breathing. This short-acting medication should stop working within 24 hours, although its effects can be longer in pets with liver or kidney disease. Published literature regarding the safety and efficacy of pimobendan in cats is relatively sparse, particularly in the subpopulation of cats with OTO. Only a single cat with multiple congenital cardiac defects (including an OTO) developed hypotension after receiving pimobendan, which resolved with discontinuation of the drug.

References

[1] Anna K. McManamey. “Pharmacokinetics of pimobendan after oral administration to dogs with myxomatous mitral valve disease.” Journal of Veterinary Internal Medicine 37 6 (2023): 2003–2010.

[2] Jessica L. Ward. “Retrospective evaluation of the safety and tolerability of pimobendan in cats with obstructive vs nonobstructive cardiomyopathy.” Journal of Veterinary Internal Medicine 34 6 (2020): 2211–2222.