Q Several months ago you published an article that talked about a medicine called pimobendan that could stave off the symptoms of congestive heart failure and thereby keep a dog with that condition healthier for a longer period of time. I have a 12-year-old beagle, Chewy, in that situation. She has been diagnosed with congestive heart failure because she has a heart murmur and an enlarged heart but does not yet have major symptoms of the disease — not really any weakness, difficulty breathing, severe loss of appetite, or cough. I showed the doctor your article, but Chewy was prescribed a drug called enalapril (5 mg) instead of pimobendan. I asked why not pimobendan, as recommended in the article, and was told that it was expensive and they would have to order it. I asked them to do so, but in the meantime gave Chewy the enalapril, which seemed to make her more active and eat more than usual. I have since received the pimobendan and started to give it as well and will take her back in a month to see if she is doing okay. What are the differences between the two drugs? I ask in part because of the cost difference. The enalapril is $21.50 and the pimobendan is $67.59.
Dear Mr. Johnson,
A Enalapril is in the category of drugs known as ACE inhibitors. ACE inhibitors have multiple mechanisms of action, including the tendency to reduce fluid and water retention by the body. That’s good because it means reduced fluid build-up in the lungs, a hallmark symptom of congestive heart failure as a result of blood flowing backward toward them rather than forward from the heart and into the rest of the body, as it’s supposed to. (That fluid build-up in the lungs is what makes it hard to breathe.) ACE inhibitors also help lower blood pressure and can help slow enlargement of the heart. A drug that can keep down blood pressure (by literally relaxing the blood vessel walls and also decreasing stress on the heart) will help attenuate the advance of the illness.
Research now strongly suggests that pimobendan can be prescribed earlier in the disease process to actually head off symptoms for an average of 16 months (according to a multi-center trial). Like enalapril, pimobendan causes relaxation of blood vessel walls, but it also works via a different mechanism. It improves the ability of the heart muscle to pump, thereby moving blood in the right direction without too much cardiac stress.
Both drugs have proven through studies to be well tolerated by dogs and to have positive effects, and both are recommended for dogs with congestive heart failure that is further along than Chewy’s. (Sometimes another ACE inhibitor may be used in place of enalpril, such as Benazepril or Lisinopril.) ACE inhbitors have not been shown to be of help in delaying disease progression at Chewy’s stage, as pimobendan has.
That said, different veterinarians approach treatment differently. Some start a dog on an ACE inhibitor a little earlier than others. It is not unheard of for enalapril to be prescribed for a dog like Chewy.
As to why your veterinarian didn’t have pimobendan readily available, it’s hard to say. It has been on the veterinary market in the U.S for about a decade, but that still makes it a relatively new drug. And the evidence that it can help significantly earlier in the disease process than other drugs has only very recently come down the research pike.
As to price, it’s affected by different factors, including whether a dog is prescribed a drug once or twice a day, whether it is being purchased from, say, the veterinary clinic or CVS, the cost of the research that it took to bring the drug to market, and so on.
Please let us know how Chewy does as he goes forward on pimobendan.