# Vetmedin Overdose in Dogs: Signs and What to Do A Vetmedin (pimobendan) overdose in dogs can cause vomiting, a racing or unusually slow heart rate, weakness, and low blood pressure. If your dog got a double dose or chewed into the bottle, call your veterinarian or a pet poison hotline right away, even if your dog seems fine. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - A single extra dose of Vetmedin is often tolerated, but a large overdose (several pills at once, or a chewed bottle) needs immediate veterinary advice. - Call your veterinarian, an emergency clinic, or a pet poison hotline before you try to make your dog vomit at home. - Save the pill bottle and count how many tablets are missing so you can tell the vet how much your dog may have eaten. - Watch for vomiting, drooling, weakness, wobbliness, a racing or very slow heartbeat, pale gums, or collapse. - Do not give another dose of Vetmedin until a veterinarian tells you to. ## What Vetmedin Is and What Veterinarians Use It For Vetmedin is the brand name for pimobendan, a prescription heart medication for dogs. It is most often used for myxomatous mitral valve disease (MMVD), the degenerative valve problem that is the most common heart disease in small and medium dogs. It is also used for dilated cardiomyopathy and other forms of heart failure. Pimobendan has been shown to delay the onset of congestive heart failure and prolong survival in dogs with MMVD [1]. Many dogs now start the drug before they ever go into heart failure, when an echocardiogram shows an enlarged heart. In one multicenter study, dogs that received pimobendan in this preclinical phase had shorter survival times after they eventually developed congestive heart failure compared with dogs that started the drug only at heart failure [2]. That finding is still being sorted out, and it does not mean the drug is harmful. It means timing and monitoring matter, and your cardiologist will weigh the pros and cons for your dog. Vetmedin comes as capsules and as an oral liquid. A study in healthy Beagle dogs found that a 1.5 mg/mL oral solution and the standard 5 mg capsules were bioequivalent, meaning they delivered similar drug levels in the blood, and both were well tolerated [3]. The liquid can make dosing easier for tiny dogs and for dogs that are hard to pill. ## How Vetmedin Works Pimobendan does two jobs at once. It makes the heart muscle contract more strongly (a positive inotropic effect), and it opens blood vessels so the heart does not have to push against as much resistance. The result is better forward blood flow and less strain on a failing heart. Part of how it works is calcium sensitizing, which means it helps the heart muscle use calcium more efficiently. It also inhibits phosphodiesterase III, an enzyme that affects how strongly and how fast the heart contracts. In a canine study of rapid atrial pacing, a model of a fast, abnormal heart rhythm, pimobendan was evaluated to see whether it improved systolic function without making myocardial injury worse [4]. That kind of research helps veterinarians understand how the drug behaves when the heart rhythm is not normal, which is relevant because a pimobendan overdose can push heart rate and rhythm in the wrong direction. ## Dosing Basics ### Who decides the dose Your veterinarian does, every time. The dose depends on your dog's weight, the stage of heart disease, kidney and liver function, and what other medications your dog takes. Never adjust the dose on your own, and never use a dose meant for another dog in the house. ### How it is given Vetmedin is usually given by mouth, with or without food. Most dogs take it twice a day, about 12 hours apart. In one study of dogs with preclinical MMVD, pimobendan was given orally at 0.25 to 0.3 mg/kg every 12 hours, and echocardiographic measures of heart enlargement improved after 7 days [1]. That range is a research dose, not a prescription for your dog. Your veterinarian will calculate the exact amount. ### What to do about a missed dose If you miss a dose and you remember within a few hours, give it. If it is almost time for the next dose, skip the missed one and go back to your normal schedule. Do not double up to catch up. If you are not sure what to do, call your veterinarian or a pet poison hotline. For general steps on handling any medication mistake, see [What to Do If Your Dog Overdoses on Medication: Emergency Steps](/knowledge/veterinary-medicine/pet-medication-guide/dog-medication-overdose-emergency-steps). ## Side Effects: Common and Serious Most dogs tolerate pimobendan well. In the bioequivalence study, both the capsule and liquid forms were well tolerated in healthy dogs [3]. Still, side effects happen, and some are serious. | Side effect | How common or serious | What to do | |---|---|---| | Vomiting, diarrhea, poor appetite | Common, usually mild | Give with a small meal. Call your vet if it lasts more than a day or your dog stops eating | | Lethargy or sleepiness | Common, usually mild | Note the timing. Call your vet if your dog is hard to rouse | | Fast or irregular heartbeat | Serious | Call your vet or an emergency clinic now | | Very slow heartbeat | Serious | Emergency. Go in now | | Weakness, wobbliness, collapse | Serious | Emergency. Go in now | | Pale or white gums | Serious (possible low blood pressure) | Emergency. Go in now | | Fainting | Serious | Emergency. Go in now | For a fuller list of expected reactions at normal doses, see [What Are the Side Effects of Vetmedin for Dogs?](/knowledge/veterinary-medicine/pet-medication-guide/vetmedin-side-effects-dogs). ## Who Should Not Take It and Drug Interactions Vetmedin is not right for every dog. Your veterinarian will avoid it or use it with caution in dogs with certain heart conditions where the drug could make an obstruction worse, in dogs with severe liver disease, and in dogs that have had a bad reaction to it before. Tell your vet about every medication, supplement, and herbal product your dog takes. Some drugs can interact with pimobendan. These include other heart medications, diuretics, and drugs that affect blood pressure or heart rhythm. Your veterinarian will review the whole list before prescribing. If your dog sees more than one clinic, make sure each one knows about all the medications. If your dog takes other medications that can be dangerous in excess, the same emergency rules apply. Two examples are anxiety medications and human pain relievers. You can read about those in [Dog Anxiety Medication Overdose: Signs and Emergency Steps](/knowledge/veterinary-medicine/anxiety-and-behavior-support/dog-anxiety-medication-overdose) and [Dog Ate Ibuprofen or Tylenol: Toxicity Signs and Emergency Treatment](/knowledge/veterinary-medicine/emergency-and-first-aid/dog-ate-ibuprofen-tylenol-toxicity-treatment). ## Vetmedin for Dogs Overdose: Signs and What to Do ### What counts as an overdose An overdose means any amount more than your dog's prescribed dose. Common situations include a double dose because two people in the house each gave a pill, a dog that chewed through a pill bottle, a dog that ate pills dropped on the floor, or a dose calculated for the wrong weight. How serious it is depends on how much your dog actually swallowed, your dog's size, and your dog's heart condition. A large dog that gets one extra tablet may have no signs at all. A small dog with heart disease that eats half a bottle is a different story. ### Signs veterinarians watch for Pimobendan increases the force of heart contractions and lowers blood pressure by widening blood vessels. Too much of it can push those effects too far. The signs vets look for fall into two groups. Heart rate signs: - A racing heartbeat (tachycardia) - An irregular rhythm - A very slow heartbeat (bradycardia), which can happen when the drug's effects overwhelm the heart's normal pacing Blood pressure and circulation signs: - Weakness or wobbliness - Collapse or fainting - Pale, white, or gray gums - Cool limbs - Fast, shallow breathing - Vomiting, drooling, or restlessness Some of these signs overlap with the symptoms of heart disease itself, which makes it hard to sort out at home. That is one reason to call instead of wait. ### What to do right now 1. Move your dog away from any remaining pills and pick them up. 2. Count the pills. Compare what is left in the bottle to what should be there so you can estimate how many were eaten. 3. Save the bottle, the label, and any chewed packaging. 4. Call your veterinarian, the nearest emergency clinic, or a pet poison hotline. Have your dog's weight, the dose on the label, and your estimate of how many pills were eaten ready. 5. Do not induce vomiting unless a veterinarian tells you to. Making a dog vomit can be dangerous, and it is the wrong move in some situations. 6. Do not give the next scheduled dose until a vet says it is safe. 7. If your dog is collapsing, having trouble breathing, or has pale gums, go to the emergency clinic now. Do not wait for a callback. ### What the veterinarian will do Your vet will ask what happened, examine your dog, and check heart rate, heart rhythm, gum color, and blood pressure. They may run blood work, including kidney and liver values, and they may place an IV for fluids. If your dog is unstable, treatment focuses on supporting blood pressure and heart rhythm. There is no specific antidote for pimobendan, so care is supportive and tailored to the signs your dog is showing. Depending on timing, your vet may also decontaminate, meaning they may induce vomiting or give activated charcoal in the clinic. ### If you are not sure whether your dog ate a pill Call anyway. A pet poison hotline can help you decide whether the amount matters. It is far better to make a phone call than to watch and wait while a dog gets sicker. ## Limitations and When to Contact a Veterinarian Individual cases need a veterinarian. No article can tell you whether your dog's specific dose, weight, and heart condition make an overdose dangerous. Your vet has the exam findings and the bloodwork, and that is what decides the plan. Contact your veterinarian the same day if: - You gave a double dose, even if your dog seems normal - Your dog vomited once or twice after a dose - Your dog seems more tired than usual - You are unsure how many pills are left in the bottle Go to an emergency clinic now if: - Your dog collapses, faints, or cannot stand - Your dog's gums are pale, white, or gray - Your dog is breathing fast or working hard to breathe - Your dog's heartbeat feels very fast, very slow, or irregular - Your dog ate a large number of tablets or chewed through a bottle Schedule a routine visit if: - Your dog has mild vomiting or appetite loss that lasts more than a day - You keep having trouble giving the medication and want to switch to the liquid form - You want to review the dose, the timing, or the refill schedule ## Frequently Asked Questions ### How much Vetmedin is too much for a dog? Any amount above your dog's prescribed dose is too much, but the risk depends on the size of the overdose and your dog's weight and heart condition. There is no single cutoff that applies to every dog. Call your veterinarian or a pet poison hotline with the dose on the label and your best estimate of how many pills were eaten. ### Can a Vetmedin overdose kill a dog? A large overdose can be life threatening because of severe low blood pressure and dangerous heart rhythm changes. The outcome depends on how much was eaten, how quickly you got help, and your dog's underlying heart disease. This is why a suspected large overdose is an emergency, not a wait and see situation. ### My dog seems fine after a double dose. Do I still need to call? Yes. Signs can take time to appear, and some of the most serious effects, like low blood pressure, are not obvious at home. A quick call lets your vet decide whether your dog needs to be seen or can be monitored at home. Keep watching for vomiting, weakness, and changes in gum color. ### Should I make my dog vomit after eating too many Vetmedin pills? No, not unless a veterinarian tells you to. Inducing vomiting at home can cause harm, and it is not the right step in every case. Your vet will decide whether decontamination is safe and useful based on how long ago the pills were eaten and how your dog is doing. ### Will my dog need to stay at the hospital? That depends on the amount eaten and the signs your dog shows. Dogs with mild exposure and normal vital signs may go home with monitoring instructions. Dogs with low blood pressure, an abnormal heart rhythm, or collapse usually need IV fluids and close monitoring in the hospital until they are stable. ## Related Articles - [Dog Anxiety Medication Overdose: Signs and Emergency Steps](/knowledge/veterinary-medicine/anxiety-and-behavior-support/dog-anxiety-medication-overdose) - [What to Do If Your Dog Overdoses on Medication: Emergency Steps](/knowledge/veterinary-medicine/pet-medication-guide/dog-medication-overdose-emergency-steps) - [What Are the Side Effects of Vetmedin for Dogs?](/knowledge/veterinary-medicine/pet-medication-guide/vetmedin-side-effects-dogs) - [Dog Ate Ibuprofen or Tylenol: Toxicity Signs and Emergency Treatment](/knowledge/veterinary-medicine/emergency-and-first-aid/dog-ate-ibuprofen-tylenol-toxicity-treatment) - [Dog Diabetes: How to Tell If Your Dog's Insulin Dose Is Too High](/knowledge/veterinary-medicine/senior-and-chronic-care/dog-diabetes-insulin-overdose-signs) - [Dog Ate Chocolate? Poisoning Signs and Emergency Steps](/knowledge/veterinary-medicine/online-vet-and-care-costs/dog-ate-chocolate-poisoning) - [What Does Vetmedin Do for Dogs With Heart Disease?](/knowledge/veterinary-medicine/pet-medication-guide/what-does-vetmedin-do-dogs) - [Enalapril for Dogs: Side Effects and What It Does](/knowledge/veterinary-medicine/pet-medication-guide/enalapril-dogs-side-effects) - [Dog Poisoning and Overdose: Home Remedies Are Not Enough](/knowledge/veterinary-medicine/toxicology-and-food-safety/dog-poisoning-overdose-home-remedy) ## References 1. [Short-term effects of pimobendan in dogs with preclinical myxomatous mitral valve disease](https://pubmed.ncbi.nlm.nih.gov/42682558/). Frontiers in veterinary science, 2026. 2. [Survival of dogs with myxomatous mitral valve disease administered preclinical pimobendan in comparison to pimobendan-naïve dogs from the onset of congestive heart failure](https://pubmed.ncbi.nlm.nih.gov/42247930/). Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology, 2026. 3. [Evaluation of bioequivalence of pimobendan oral solution and pimobendan oral capsules in healthy Beagle dogs](https://pubmed.ncbi.nlm.nih.gov/40245826/). Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology, 2025. 4. [Effect of pimobendan on myocardial injury and systolic dysfunction in a canine model of supraventricular tachyarrhythmia](https://pubmed.ncbi.nlm.nih.gov/41062284/). The Journal of veterinary medical science, 2025. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information)