If your dog eats a lisinopril pill, the main danger is a dangerous drop in blood pressure, which can secondarily harm the kidneys. A single low-dose tablet often causes only mild symptoms in a medium or large dog, but higher doses or smaller dogs face greater risk. You should call your veterinarian or an animal poison control hotline right away, even if your dog seems fine at first.
How Lisinopril Affects Dogs
Lisinopril is a blood pressure medication (an ACE inhibitor) that works by relaxing blood vessels and reducing the force the heart pumps against. Veterinarians actually prescribe ACE inhibitors to dogs for congestive heart failure, so the drug itself isn’t foreign to a dog’s body. The problem is dose. A pill meant to lower blood pressure in a 180-pound human can cause a far more dramatic drop in a 20-pound dog.
When blood pressure falls too low, organs don’t get enough blood flow. The kidneys are especially vulnerable. If low blood pressure persists, it can lead to acute kidney injury, where the kidneys suddenly lose the ability to filter waste properly. The body’s electrolyte balance can also shift, with potassium levels rising to dangerous levels and blood sugar potentially dropping.
How Much Is Dangerous
Toxicity in dogs generally becomes a concern when the ingested dose exceeds 10 to 20 times a normal therapeutic dose. Lisinopril tablets come in strengths of 2.5, 5, 10, 20, 30, and 40 mg. For context, a therapeutic dose for a dog is roughly 0.5 mg per kilogram of body weight, so a 10 kg (22-pound) dog would normally take about 5 mg.
That means a single 5 mg tablet is unlikely to cause serious harm in a medium-sized dog, since it’s within the therapeutic range. But if that same 22-pound dog swallows a 40 mg tablet, or multiple pills, the math changes quickly. Small dogs and puppies are at the highest risk because even a standard human dose represents a much larger amount relative to their body weight.
When you call your vet, have the medication bottle handy so you can tell them the tablet strength and roughly how many pills are missing. This helps them calculate the dose your dog received and decide how urgently to intervene.
Symptoms to Watch For
Signs of lisinopril overdose typically appear within a few hours of ingestion. The most common symptoms include:
- Vomiting
- Weakness or lethargy, from low blood pressure reducing blood flow to muscles and the brain
- Pale gums, a visible sign of poor circulation
- Abnormal heart rate, either unusually fast or slow
A dog with mild exposure might seem a little sluggish or have a brief episode of vomiting but recover on its own. A dog with a more significant overdose can become wobbly, collapse, or stop producing urine, all signs that blood pressure has dropped to a dangerous level and organs are being affected.
What to Do Right Away
Keep your dog calm and make sure they have access to water. Do not try to induce vomiting on your own unless a veterinarian specifically tells you to, since improper technique or timing can cause more harm than good. Call your vet, an emergency animal hospital, or the ASPCA Animal Poison Control Center (888-426-4435) immediately.
Even if your dog seems perfectly normal, it’s worth making the call. Symptoms can take a few hours to show up, and early intervention is far easier than treating a crisis once blood pressure has already plummeted.
What Happens at the Vet
If the ingestion happened recently, your vet may induce vomiting or administer activated charcoal to limit how much of the drug gets absorbed. Beyond that, treatment is based on your dog’s blood pressure, heart rate, and blood work.
The most common treatment for low blood pressure from ACE inhibitor overdose is intravenous fluids, which is often enough to stabilize circulation. If the heart rate drops too low, medication can be given to bring it back up. In more severe cases where blood pressure doesn’t respond to fluids alone, your dog may need stronger medications delivered through a continuous IV drip to support heart function and maintain circulation.
Vets will monitor kidney function for one to two days if blood pressure dropped significantly, since the kidneys are the organ most likely to suffer lasting damage from prolonged low blood flow. Electrolyte levels, particularly potassium, are also tracked throughout the hospital stay. If blood sugar drops, that’s corrected with a sugar-containing IV solution.
Recovery and Outlook
Most dogs that receive timely treatment recover well. Low blood pressure from ACE inhibitor ingestion generally responds to IV fluids, making it one of the more treatable medication overdoses in veterinary toxicology. The key factor is how quickly treatment begins and how large the dose was relative to the dog’s size.
Dogs that ingested a small amount and showed only mild symptoms may need nothing more than monitoring at home. Dogs that needed hospitalization typically spend one to two days under observation while their blood pressure, kidney values, and electrolytes stabilize. Permanent kidney damage is possible but uncommon when treatment starts before prolonged low blood pressure sets in.
Dogs with pre-existing kidney disease, heart conditions, or those already taking medications that lower blood pressure are at higher risk of complications, since their systems have less margin to absorb the effects of an overdose. If your dog falls into any of these categories, treat even a small ingestion as an emergency.