Your Dog Got Into Your Antidepressants. Here's What Happens Next.

If your dog just got into your antidepressants, 5-HTP supplements, or any medication that affects brain chemistry, stop reading and call your vet or a poison control hotline right now. Serotonin syndrome is a genuine emergency, and the faster you act, the better the outcome.

If you’re here because you’re trying to understand what’s happening or what comes next, this guide covers everything: what causes it, what symptoms to watch for, how it’s treated, and how to prevent it from happening again.

If your dog just ingested something: do this first

If you’re here because something just happened, skip everything else and follow these steps right now.

1. Stay calm and note the time. Write down or take a photo of what was ingested and how much. Check the bottle for the number of pills remaining if you can.
2. Call poison control immediately. ASPCA Animal Poison Control Center: 888-426-4435 (available 24/7, fee may apply). Pet Poison Helpline: 855-764-7661 (available 24/7, fee may apply).
3. Follow their instructions. With serotonin-affecting substances, the answer is almost always to go to the emergency vet right away.
4. Bring the packaging. Take the bottle or supplement container with you so the vet knows exactly what your dog ingested and how much.
5. Do not induce vomiting on your own unless poison control specifically tells you to. For some substances, this makes things worse.

The rest of this article is here when you need it. Right now, make the call.

What causes serotonin syndrome in dogs?

Serotonin toxicity almost always comes from one of two situations: your dog ate something they shouldn’t have, or two medications that both raise serotonin levels were given too close together.

Culprit	What to know
SSRIs (fluoxetine, sertraline)	Human antidepressants that slow the removal of serotonin from the brain. Among the most frequently reported causes of accidental ingestion in dogs.
Trazodone	Sometimes prescribed to dogs for anxiety, but risky in overdose or when combined with other serotonin-affecting drugs.
MAOIs (selegiline, older antidepressants)	Block the breakdown of serotonin entirely. Also found in some flea and tick preventatives.
5-HTP	A popular human supplement for sleep and mood that converts directly into serotonin. Dogs are especially sensitive, and even small amounts can trigger toxicity.
SAM-e	Sold as a liver and mood supplement for both humans and pets. Too much can contribute to the problem.
St. John’s Wort	An herbal supplement that acts similarly to an SSRI in the body and can cause or worsen serotonin syndrome.
Drug combinations	A dog on fluoxetine who gets a dose of trazodone, for example, can tip into serotonin syndrome even when both medications are within a normal dose range.

What are the symptoms of serotonin syndrome in dogs?

Symptoms usually appear within one to four hours of ingestion and can get worse fast. Here’s what to watch for:

• Agitation or restlessness: Your dog can’t settle, paces, or seems panicked.
• Tremors: Shaking or muscle twitching, sometimes all over the body.
• Elevated heart rate: A racing heartbeat you might notice if you place a hand on their chest.
• Hyperthermia: A dangerously high body temperature over 104°F, which can cause organ damage if it stays elevated.
• Dilated pupils: Their eyes look wider or darker than usual.
• Disorientation or confusion: Stumbling, seeming drunk, or not responding to their name normally.
• Vocalizing: Whining, crying, or barking in a way that seems distressed and out of character.
• Vomiting or diarrhea: Especially in the early stages.
• Seizures: A sign the situation has become critical. Get to an emergency vet immediately.

Not every dog will show every symptom, and mild cases can look like general anxiety or an upset stomach. If you have any reason to suspect a medication or supplement was involved, don’t wait to see if it gets worse.

Diagnosis and treatment

There’s no single test that confirms serotonin syndrome. Your vet will diagnose it based on what your dog was exposed to, their symptoms, and a physical exam.

Decontamination

If ingestion was recent, usually within one to two hours, your vet may induce vomiting or give activated charcoal, a substance that binds to toxins in the gut and helps prevent more from being absorbed. This is most effective early, which is one reason calling immediately matters so much.

Cyproheptadine

The main medication used to treat serotonin syndrome in dogs is cyproheptadine, an antihistamine that blocks serotonin receptors. It doesn’t remove the excess serotonin, but it stops serotonin from binding and causing further harm. Think of it like changing the locks so the key can’t do any more damage.

Supportive care

Depending on severity, your dog may need IV fluids, medications to manage tremors or seizures, active cooling if their body temperature is dangerously high, and close monitoring in a hospital setting. Most dogs who receive prompt treatment recover fully. Severe cases, particularly those involving seizures or prolonged hyperthermia, carry a more serious risk.

There’s no single antidote that reverses serotonin syndrome completely, but with fast, appropriate treatment, most dogs recover. The goal is stopping further absorption, blocking the excess serotonin’s effects, and supporting the body while it clears the drug.

Your household medication and supplement safety guide

Serotonin syndrome is largely preventable. Here’s how to reduce the risk in your home.

High-risk items to store safely away from dogs

• Any SSRI antidepressant (fluoxetine, sertraline, escitalopram, paroxetine)
• Trazodone, even the bottle prescribed for your dog if dosed incorrectly
• MAOI antidepressants and selegiline-based pet medications
• 5-HTP supplements in any dose or format
• SAM-e supplements, including pet-specific ones if given in excess
• St. John’s Wort in any form
• Tramadol and other opioids that also affect serotonin levels
• Dextromethorphan, found in many over-the-counter cold medications

Storage habits that actually help

Keep all medications in a closed cabinet, not on a countertop or nightstand. Never leave pill bottles on a coffee table, even briefly. Be especially careful with weekly pill organizers, which are easy for dogs to chew open. Store your dog’s medications separately from human medications to avoid mix-ups. And check the floor after taking any medication. Dropped pills happen more than people realize.

Does pet insurance cover serotonin syndrome in dogs

Yes, accidental ingestion and toxicity are eligible for coverage under a Lemonade Pet accident and illness policy, as long as the condition isn’t pre-existing. Emergency treatment for serotonin toxicity, including decontamination, hospitalization, IV fluids, cyproheptadine, and seizure management, can cost anywhere from several hundred to several thousand dollars depending on how long your dog needs to be monitored.

A policy that’s already in place when your dog gets into your nightstand drawer is the one that can actually help. Getting coverage in place before something happens is what makes it useful when you need it most.

Before we go

Serotonin syndrome is scary, but it’s also very treatable when you act fast. If your dog is showing symptoms right now, close this tab and call poison control or your emergency vet. If you’re reading this as a precaution, take five minutes to secure your medications and save those poison control numbers in your phone. Both of those things cost nothing and could save your dog’s life.

And if you want to make sure an emergency vet visit doesn’t derail your finances, it’s worth looking into coverage now. 👉

Frequently Asked Questions

A few quick words, because we <3 our lawyers: This post is general in nature, and any statement in it doesn’t alter the terms, conditions, exclusions, or limitations of the policies issued, which differ according to your state of residence. You’re encouraged to discuss your specific circumstances with your own professional advisors. The purpose of this post is merely to provide you with info and insights you can use to make such discussions more productive! Naturally, all comments by, or references to, third parties represent their own views, and Lemonade assumes no responsibility for them. Coverage may not be available in all states. Please note that statements about coverages, policy management, claims processes, Giveback, and customer support apply to policies underwritten by Lemonade Insurance Company or Metromile Insurance Company, a Lemonade company, sold by Lemonade Insurance Agency, LLC.  The statements do not apply to policies underwritten by other carriers.