Pimobendan Poisoning in Dogs

Pimobendan is a drug used for dogs to increase their heart’s pumping ability, which is usually given to dogs with certain kinds of heart disease. Some of these are congestive heart failure (CHF), dilated cardiomyopathy, and mitral valve insufficiency. It is an inotrope used for congestive heart disease and heart failure in dogs. Pimobendan works by slowing the function of phosphodiesterase enzymes that open the blood vessels and makes the proteins in the heart more sensitive to calcium, which helps it to contract more effectively. It is usually given with other medications like digoxin and ACE inhibitors. Because this medication has been made to taste good to your dog, and it comes in chewable tablets, a toxic dosage of pimobendan is possible if your dog has access.

Pimobendan (Vetmedin) is a commonly prescribed heart medication used by veterinarians. In some cases, pimobendan has been known to cause rapid heart rate, vomiting, diarrhea, nervousness, collapse, convulsions, and possibly death if not treated right away. In addition, if given to a dog without a heart condition, the effects can be life-threatening immediately. This type of drug toxicity can be mistaken for other illnesses, such as a virus, and may be overlooked until it is too late. That is why it is important to see your veterinarian right away if you even suspect that your dog has ingested pimobendan. There are two types of pimobendan poisoning, which are acute (taking a large dose causing immediate toxicosis) or chronic (taking small amounts on a regular basis, causing a gradual toxicosis).

Your dog may not show any signs of toxicity right away, and some of the mild symptoms, such as stomach upset and weakness, may be overlooked as a virus or anxiety. However, if your dog has gotten into the medication, you are likely to notice that the bottle or blister pack the pills came in are on the floor or chewed on. Anytime you think your dog may have ingested a medication of any kind; it is vital that you call your veterinarian or get your dog to a pet hospital or clinic. Some of the most commonly reported symptoms are:

• Allergic reaction (breathing difficulty, hives)
• Collapse
• Cough
• Coughing
• Dark sticky stool (melena)
• Dehydration
• Depression
• Diarrhea
• Elevated heart rate
• Fainting (syncope)
• Fluid accumulation in the lungs and/or abdomen (ascites)
• Gagging
• Heart murmur
• Increased respiratory rate
• Increased thirst and urination
• Irregular pulse
• Itchy skin (pruritus)
• Lethargy
• Loss of appetite
• Loss of bodily movements (ataxia)
• Low blood pressure
• Restlessness
• Seizures
• Shaking
• Staggering
• Sudden death
• Trembling
• Urinary accidents
• Vomiting
• Weak pulse
• Weakness
• Weight loss

 Types

• Acute pimobendan poisoning is caused by an ingestion of a large amount of the drug at once (such as with accidental overdose or if your dog gets into the medication
• Chronic pimobendan poisoning is caused by a small amount given on a regular basis

• Accidental overdose by owner
• Dog ingesting medication left out in his reach
• Giving the medication to the wrong dog

A full body examination will be done, which will include abdominal palpation, vision and hearing check, reflexes, heart rate, oxygen level, blood pressure, and body temperature. The veterinarian will also need your dog’s complete medical history, recent illnesses, injuries, abnormal behavior, and vaccination records.

Some laboratory tests will also be performed, such as serum electrolyte levels, protein and glucose, complete blood count (CBC), urinalysis, and fecal examination. The veterinarian will be looking for a decrease in the platelet count, increased phosphates, high blood glucose and liver enzymes, and an increase in protein in the urine and blood. 

Chest and abdominal images through radiographs (x-rays) may be done to get a look at the heart and lungs. If the veterinarian suspects damage, CT scans, ultrasound, and possibly an MRI may be used to get a better view. An electrocardiogram (ECG) can be done to measure the heart’s electrical and muscular activity.

The treatment for acute pimobendan poisoning is to induce vomiting and administer activated charcoal to bind with the medication so it can be eliminated more safely. In cases of chronic pimobendan poisoning, the damage from the toxicity has already been done, so the treatment will depend on which organs are affected by the drug. 

If your dog gets treatment right away for acute pimobendan poisoning, chances for recovery are good, depending on the dose taken and health of your dog. However, in the case of chronic poisoning, recovery chances are not good and will depend on the amount of damage done by the medication. To keep this from happening again, be sure to keep this and all other medication out of your dog’s reach.

Pimobendan poisoning can be expensive to treat. To avoid high vet care expenses, secure pet health insurance today. The sooner you insure your pet, the more protection you’ll have from unexpected vet costs.