Dog & cat health · Vet-reviewed guide

Trazodone for Dogs Side Effects: What to Watch

The main trazodone side effect is drowsiness, which is usually the point rather than a problem. Here's what's expected and the rare signs that aren't.

The most common trazodone side effect in dogs is sedation, which is expected and not a reason to stop, along with occasional stomach upset or wobbliness. Studies suggest around 80% of dogs have no negative effects. Rare serious signs need a vet. Always use the dose your veterinarian sets.

Emergency: High fever, tremors, muscle rigidity, severe agitation, or seizures can signal serotonin syndrome, especially if trazodone was combined with another serotonin drug (like an SSRI). Get emergency veterinary care immediately.

About trazodone for dogs & cats: this is a prescription medication your veterinarian can prescribe. Read our guide, or ask us if you need help sourcing it.

Common, expected side effects

• Sedation and drowsiness (the intended calming effect; not a reason to stop)
• Mild stomach upset, diarrhea, or nausea
• Wobbliness (ataxia) or, occasionally, increased appetite²

Around 80% of dogs experience no negative side effects, per veterinary data.² A common mistake is stopping the medication because a dog seems "too sleepy" — mild sedation is expected. Ask your vet before changing anything.

The serious risk: serotonin syndrome

Because trazodone raises serotonin, combining it with other serotonin-active drugs, especially SSRIs like fluoxetine or MAOIs, can cause serotonin syndrome.¹ Warning signs are high fever, tremors, muscle rigidity, agitation, and seizures. This is an emergency. The rule: never combine behavioral medications without direct veterinary supervision.

Other cautions

Trazodone should be used carefully in dogs with certain heart conditions or aggression, and rare reactions include cardiac arrhythmias and allergic reactions.² Tell your vet about every medication and supplement your dog takes so interactions are checked before the first dose.

When to call the vet

Call your vet for anything beyond mild sedation and brief stomach upset, and seek emergency care for the serotonin-syndrome signs above.¹ Our vets review your dog's full medication list when prescribing. See how our vet prescription service works. For the overview, see trazodone for dogs.