Cardiology Vets Evaluate 'Rescue" Drug Pimobendan

Pimobendan is a drug used in Canada, Australia, and Europe to treat heart failure in dogs. It is marketed by the pharmaceutical company Boehringer Ingelheim under the brand name Vetmedin. In the US, Pimobendan is currently undergoing FDA clinical trials, and has not been approved for use. This drug has been a topic of ongoing conversation among veterinary cardiologists, veterinarians, and dog owners for the past few years.

The purpose of this brief article is to put forth some opinions to the Irish Wolfhound community about the pros and cons of Pimobendan. Since the drug is still under study, both for effectiveness and for safety, there is much uncertainty about it, and what we think we know at this point may still be incorrect.  The opinions written are those of the author and reflect what is known currently. Additional studies in the United States and abroad may reveal new or different information over time.

My practice has been involved with the FDA clinical trials to see if Pimobendan should be approved for use here in the United States. I feel this medication is quite beneficial in certain circumstances. However, it is not for use in all dogs with heart disease. My practice has reserved the use of Pimobendan to use as a rescue drug in patients with advanced heart disease and congestive heart failure. We prefer to use more conventional medications that are FDA approved, such as Benazepril Digoxin, Enalapril, Lasix, Spironolactone, beta-blockers, etc., as starting points in treatment. These drugs may slow progression of disease and help the dog feel better,. However, heart disease does sometime progress in the face of treatment. If a patient is no longer responding to standard medications, then we may speak with the owner about the use of Pimobendan and its pros and cons.

On the positive side, Pimobendan will usually improve a patientʼs heart failure symptoms when combined with other cardiac medications. It may also improve a patientʼs NYHA heart failure score, i.e. improve exercise capacity/demeanor, etc. I have seen this drug improve some dogsʼ appetites as well. Lastly, it may also improve overall survival time for patients in congestive heart failure. However, I feel that, with the studies still in progress, it is still too soon to make blanket statements about the positive effects of Pimobendan.

What are the down sides to this medication, and why donʼt we place every dog with heart disease on this medication? Researchers have found that Pimobendan may increase the risk of sudden death in canine patients. Interactions may exist between other heart medicines, such as beta-blockers, and Pimobendan.  My practice has, in fact, seen sudden deaths in patients treated with Dobutamine that were taking Pimobendan. Also, we have seen some increase in ventricular arrhythmias in patients treated with Pimobendan. This is a serious finding, because some of these arrhythmias are difficult to treat and may be fatal in themselves.

In summary, Pimobendan does appear to offer some benefits for canine patients with advanced heart disease and congestive heart failure. However, this drug has the potential for severe side effects, including sudden death. In my opinion, “Pimo” should be reserved for patients whose advanced heart disease is no longer responding to more well-understood medicines that have been used long term in veterinary cardiology. Further studies are required with Pimobendan in order to make more concrete and definitive recommendations for its overall usage.  If your veterinarian or veterinary cardiologist does wish to use Pimobendan legally in the United States, he or she must get approval from the FDA to import the drug from abroad. FDA approval can take up to four weeks to secure. Appropriate documentation of this approval has to accompany the shipment; otherwise, US Customs may seize the package.

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