What is the recommended Pimobendan dosage for senior dogs with Stage B2 MMVR?

• A. 0.25-0.3 mg/kg PO q12
• B. 1.0 mg/kg PO daily
• C. 0.05 mg/kg PO q24
• D. 0.5 mg/kg PO q8

Answer: (A)

Pimobendan dosing for senior dogs with Stage B2 MMVR uses a low, steady dose given twice daily. The standard recommendation is 0.25 mg/kg taken by mouth every 12 hours. This dosing comes from studies showing that this regimen helps improve cardiac function and, importantly, delays the onset of congestive heart failure in dogs with mitral valve disease who have cardiomegaly but no heartbeat-related symptoms yet.

Understanding the context helps: Stage B2 means the dog is not yet in heart failure, but there is radiographic or echocardiographic evidence of cardiac enlargement due to MMVD. Pimobendan acts as an inodilator—it increases heart muscle contractility in a calcium-dependent way and dilates vessels to reduce the workload on the heart. This combination supports better forward blood flow and can slow the progression to symptomatic disease.

Other dosing options fall outside this proven regimen: they would either under-treat, risking insufficient benefit, or over-treat, increasing the chance of adverse effects. Therefore, the recommended approach remains 0.25 mg/kg PO every 12 hours.