Pimobendan (Vetmedin®) is a heart medication that is becoming a frequently used drug for dogs with heart disease. It is approved for use in the United States for dogs with congestive heart failure (CHF) caused by either dilated cardiomyopathy or mitral valve disease.
Though pimobendan is only approved for use in dogs, it is sometimes used off-label in cats as well to treat congestive heart failure, especially in cases where improvement of the ability of the heart muscle to contract is beneficial. However, its use in cats is still somewhat controversial.
How Pimobendan (Vetmedin®) Works in Congestive Heart Failure for Dogs and Cats
Pimobendan has two different methods of improving the heart's function. It acts on the heart muscle itself to improve its ability to contract normally. This is referred to as an inotropic function. It also dilates the blood vessels throughout the rest of the body, which provides less resistance to blood flow and makes it easier for the heart to pump the blood to where it needs to go.
When Should Pimobendan Be Used for Dogs and Cats?
Most veterinarians prefer to administer pimobendan only to dogs that are suffering from congestive heart failure. However, a few sometimes recommend giving the medication once heart disease is detected but before congestive heart failure has occurred. This use is still controversial and may or may not be effective in slowing the progress of disease.
Because pimobendan is not currently labelled for use in cats, its use is controversial. Some veterinarians have used it successfully. However, it is contraindicated in some types of heart disease that are common in cats (such as hypertrophic cardiomyopathy or HCM.)
Are There Any Times When Pimobendan Should Not Be Used?
Pimobendan is contraindicated in cases of hypertrophic cardiomyopathy, aortic stenosis or other types of heart disease in which increasing the amount of blood which has to be pumped by the ventricles of the heart is dangerous for the pet.
Pimobendan should also be used with caution in animals with cardiac arrhythmias, especially if the arrhythmias are not well-controlled.
If your pet is sensitive to the medication, he should not receive pimobendan.
In addition, according to the label for pimobendan, it has not been fully evaluated "in dogs younger than 6 months of age, dogs with congenital heart defects, diabetes mellitus or other serious metabolic diseases, dogs used for breeding, or pregnant or lactating bitches."
Potential Side Effects of Pimobendan
Potential side effects that have been documented with pimobendan include lack of appetite, depression, diarrhea, difficulty breathing, weakness, incoordination, azotemia (an increase in nitrogen-based waste products in the blood stream), fluid build-up in the chest cavity, fainting, coughing, a heart murmur and sudden death. Some of these "adverse reactions" may actually be due to heart disease rather than a result of giving the pimobendan.
There is some concern that pimobendan may also increase the risk of arrhythmias. However, because heart disease can cause arrhythmias as well, it is difficult to determine whether the arrhythmia is a direct result of the pimobendan or simply a manifestation of the dog's heart disease.
Pimobendan (Vetmedin®) is a drug that is approved for use in dogs with congestive heart failure due to dilated cardiomyopathy or mitral valve disease. It is sometimes used in cats but its use in cats is more controversial than its use in dogs.