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By Marc Brannigan and Natalie Mondine, co-founders of HempMy Pet · Published September 28, 2026 · Last reviewed September 28, 2026
We have grown, formulated and bottled organic full-spectrum hemp oil for pets on our own Colorado farm since 2016, and we funded two university clinical trials using our own oil. We are not veterinarians. Everything below comes from the published canine literature, cited at the end. It is not a reason to stop your dog's medication.
Trazodone is the drug most vets reach for when a dog cannot cope with a car ride, a thunderstorm, a grooming appointment or eight weeks of crate rest after surgery. It is cheap, it has a wide safety margin, and unlike several other drugs in this category, it actually works — that part is settled by blinded, placebo-controlled research in dogs.
What is not settled, and what almost no owner-facing page mentions, is the second half of the same research.
Trazodone measurably reduces stress in dogs — lower cortisol, fewer anxiety behaviours, better anxiety scores in a placebo-controlled trial. In that same trial, gabapentin did nothing at all.
But two separate blinded studies also found that trazodone raises heart rate and lowers heart rate variability. A dog that looks calmer is not necessarily a dog whose cardiovascular system has settled. If your dog has a heart condition, that is a sentence worth taking to your vet.
What Trazodone Is
Trazodone is a serotonin antagonist and reuptake inhibitor — a SARI — originally developed as a human antidepressant. In dogs it is used off-label, like gabapentin and tramadol, which is routine in veterinary medicine but means there is no canine approval behind the label.
Vets prescribe it in two distinct ways, and the distinction matters:
- Situationally — one dose given one to two hours before a known stressor. Vet visits, car travel, fireworks, nail trims, guests.
- Daily — often after orthopaedic surgery, to make weeks of enforced confinement tolerable, or as an add-on to a longer-term behaviour plan.
The evidence is much stronger for the first use than the second.
Does Trazodone Actually Work?
For situational stress, yes — and the evidence is better than for most drugs in this category.
A 2026 blinded, placebo-controlled trial in Frontiers in Veterinary Science took 36 Beagles, screened them on their baseline cortisol response to a road-travel test, and randomly assigned them to trazodone, gabapentin, or placebo — one dose, two hours before travel.
Trazodone significantly reduced serum cortisol, lip licking frequency and scores, global anxiety scores, urination, yawning, and restlessness. That is a broad and consistent result across both a hormone measure and independent behavioural scoring.
Gabapentin, in the same trial, produced no difference from placebo on any measure. If your dog is on gabapentin for travel anxiety specifically, that is worth raising — we cover it in our guide to gabapentin for dogs and its side effects.
For the daily, longer-term use the picture is thinner. The foundational canine paper is a 2009 JAVMA retrospective review of 56 dogs treated at a referral behaviour clinic, all of them already on other behavioural drugs. It found trazodone well tolerated across a wide dose range and helpful as an add-on — but it is a chart review, not a controlled trial, and the authors said so themselves: further controlled studies of dose range, efficacy and safety are needed. Sixteen years later, that is still largely true for daily use.
The Heart-Rate Finding
Here is the part we think owners are entitled to know.
In the travel trial above, mean heart rate was significantly higher after trazodone than after gabapentin, both before and during the travel test — in the very dogs whose cortisol and anxiety behaviours had dropped.
That is not an isolated result. A 2025 study in the Journal of Veterinary Cardiology put 24-hour Holter monitors on 20 healthy client-owned dogs in a double-blind, placebo-controlled crossover. Dogs on trazodone had higher average heart rates (P = 0.035), higher minimum heart rates (P < 0.001), and reduced heart rate variability (P < 0.001) — while their owners scored them as calmer (P < 0.001).
The reassuring part: no effect on the QT interval, the measure most associated with dangerous arrhythmias, in that cohort of healthy dogs. The authors suggest the heart-rate change may come from an anticholinergic effect, or from a reflex response to a drop in blood pressure.
There is also a 2026 case report of a 14-year-old Toy Poodle who developed a previously undocumented heart murmur and transient echocardiographic changes about an hour after a pre-anaesthetic dose. Elective surgery was postponed and the changes resolved. One dog is one dog — but combined with the two controlled studies, it is a coherent picture rather than a fluke.
What to do with this. Not panic. Most dogs take trazodone without any problem, and VCA's own monograph lists arrhythmias as a possible effect — it simply does not explain why. But if your dog has a known heart murmur, heart disease, or is elderly and heading for anaesthesia, name this specifically to your vet. It is a conversation, not a contraindication.
Side Effects of Trazodone in Dogs
- Sedation — the most common, and usually the point.
- Ataxia — wobbliness, most noticeable on stairs and slick floors.
- Stomach upset — vomiting, gagging, occasionally colitis. Giving it with food helps.
- Dilated pupils.
- Increased appetite.
- Faster heart rate and reduced heart rate variability, as above.
- Priapism — a persistent erection, rare but a genuine emergency in intact males.
The paradoxical reaction
A minority of dogs become more anxious, agitated or aggressive on trazodone rather than calmer. VCA lists increased anxiety and aggression among its possible effects. This is not a failure of the dose — it is a different response to the drug, and increasing the amount usually makes it worse.
If your dog got edgier rather than calmer, stop guessing and call your vet. That is a reason to change drugs, not to push through.
Serotonin syndrome — the one that is genuinely dangerous
Trazodone acts on serotonin. Combining it with other serotonergic drugs can push serotonin too high, which is a medical emergency.
The drugs that matter: tramadol, SSRIs such as fluoxetine, other behavioural medications, and MAO inhibitors including selegiline — that last combination should not be used at all.
The tramadol overlap is worth naming twice, because it is common. A dog with arthritis who is also anxious can easily end up with tramadol from one conversation and trazodone from another. Our guide to tramadol for dogs covers why that drug may be doing less than you think in the first place — which makes the risk harder to justify.
Signs of serotonin syndrome: agitation, tremors or muscle twitching, a racing heart, vomiting and diarrhoea, high body temperature, disorientation, and in severe cases seizures. This is an emergency-vet call, not a morning-appointment call.
When Trazodone Should Be Avoided
- Dogs on MAO inhibitors such as selegiline.
- Dogs on other serotonergic drugs, unless your vet has weighed it deliberately.
- Dogs with significant liver or kidney disease, where clearance is impaired.
- Dogs with known heart disease — not forbidden, but a conversation worth having given the heart-rate data.
- Dogs with a history of paradoxical reactions to it.
- Pregnant or nursing dogs, where safety is not established.
How to Give It Properly
- For situational use, time it. Give it roughly one to two hours before the stressor — that is the window the trial used. Giving it as the car pulls out is too late.
- Do a trial run. Test the first dose on a quiet day at home, not on the morning of a long drive. You want to know how your dog responds before it matters.
- Give it with food to reduce nausea.
- Write down what you see — sedation level, steadiness, appetite, and whether the dog seemed calmer or edgier. The paradoxical reaction shows up early.
- Tell your vet every single thing your dog takes, including supplements, because of the serotonin risk.
- Never stop daily trazodone abruptly after long-term use. Ask for a taper.
- Mention any heart history before a pre-anaesthetic dose.
Can Hemp Be Given Alongside Trazodone?
The honest answer has two halves.
On drug levels: the canine enzyme research did not flag this combination. The 2024 study that tested CBD against canine liver enzymes found inhibition of the pathways that clear tramadol, and no meaningful inhibition of CYP3A12 — the canine counterpart to the human enzyme every generic warning list is built on. Trazodone was not among the drugs it identified as a concern.
On effect: both can make a dog drowsy, and that stacks. That is a reason to start hemp at a low serving and watch the first two weeks, not a reason to assume danger. We went through the whole picture drug by drug in our guide to CBD and your dog's medications.
What we will not tell you is that hemp replaces trazodone for a panicking dog. Our own research was in dogs with chronic joint discomfort, not situational anxiety, and we are not going to stretch it. If your dog is genuinely terrified of car travel, trazodone has placebo-controlled evidence behind it and our oil does not.
Full-spectrum extract, grown and bottled on our own Colorado farm using organic practices — the same oil given to the 37 dogs in the 90-day study. Third-party tested, Certificate of Analysis in every order. $99
Shop the 1000mg Oil → See the StudyQuestions Worth Asking Your Vet
- Is this for a specific event, or are we using it daily? What is the plan for stopping?
- Given my dog's age and heart history, does the heart-rate data change anything here?
- Is my dog on anything else that acts on serotonin?
- What should I do if he gets more wound up rather than calmer?
- Can we do a trial dose at home before the day it matters?
Frequently Asked Questions
Does trazodone actually work for dogs?
For situational stress, yes. In a 2026 blinded placebo-controlled trial in 36 dogs, a single dose given two hours before road travel significantly reduced serum cortisol, lip licking, global anxiety scores, urination, yawning and restlessness. Gabapentin in the same trial showed no difference from placebo. Evidence for long-term daily use is much weaker — the foundational canine paper is a 56-dog retrospective chart review.
Does trazodone affect a dog's heart?
Yes. Two separate blinded studies found trazodone raises heart rate and reduces heart rate variability in dogs, even while the dogs appear calmer. No effect on the QT interval was found in healthy dogs. If your dog has known heart disease or is elderly and facing anaesthesia, raise this specifically with your veterinarian.
How long does trazodone take to work in a dog?
Roughly one to two hours, which is why situational doses are given that far ahead of the stressor rather than at the moment it starts.
Can trazodone make a dog more anxious or aggressive?
Yes, in a minority of dogs. Increased anxiety and aggression are recognised paradoxical reactions. Raising the dose usually makes it worse. If your dog got edgier rather than calmer, contact your veterinarian rather than adjusting it yourself.
What should not be given with trazodone?
MAO inhibitors such as selegiline should not be combined with it at all. Tramadol, SSRIs such as fluoxetine, and other serotonergic behaviour medications raise the risk of serotonin syndrome and require deliberate veterinary judgement. Tell your vet about every medication and supplement your dog takes.
Can my dog take hemp or CBD with trazodone?
Ask your veterinarian. The canine enzyme research did not flag this combination on drug levels — it flagged tramadol. The practical consideration is additive drowsiness, so start hemp at a low serving and watch the first two weeks.
Can I stop my dog's trazodone?
A single situational dose needs no taper. After long-term daily use, do not stop abruptly — ask your veterinarian for a taper schedule.
Is trazodone safe for long-term use in dogs?
It is widely used long-term and generally well tolerated, but the supporting canine evidence for daily use is a retrospective case series rather than a controlled trial, and the authors of that paper explicitly called for controlled studies of dose range, efficacy and safety. That is a reason to reassess periodically rather than refill indefinitely.
The same full-spectrum oil that went through two university clinical trials. Start low, go slow, and tell your veterinarian what you are giving.
How We Sourced This Article
- Acute trazodone administration reduces behavioral and physiological indicators of travel-induced anxiety in dogs. Frontiers in Veterinary Science. 2026;13:1851849. PubMed. 36 Beagles, blinded placebo-controlled. Source for the efficacy result, the higher heart rate, and gabapentin showing no difference from placebo.
- Effect of trazodone on heart rate, heart rate variability, and QT-intervals in dogs. Journal of Veterinary Cardiology. 2025;61:20–28. PubMed. 20 dogs, double-blind placebo-controlled crossover with 24-hour Holter. Source for the heart-rate and HRV figures and the absence of a QT effect.
- Gruen ME, Sherman BL. Use of trazodone as an adjunctive agent in the treatment of canine anxiety disorders: 56 cases (1995–2007). J Am Vet Med Assoc. 2009;233:1902–7. PubMed. The foundational canine paper; a retrospective case series whose authors called for controlled studies.
- Transient echocardiographic and cardiovascular changes temporally associated with trazodone administration in a geriatric dog. Veterinary Anaesthesia and Analgesia. 2026;53:101285. PubMed. Single case report, included as context rather than evidence of frequency.
- VCA Animal Hospitals — Trazodone monograph. Source for the side-effect list, the paradoxical reactions, priapism, and the serotonin syndrome and MAO inhibitor warnings.
- Court MH, et al. Cannabidiol and cannabidiolic acid: preliminary in vitro evaluation of drug–drug interactions involving canine cytochrome P-450. J Vet Pharmacol Ther. 2024;47:1–13. PubMed. Source for which drug the canine enzyme work actually flagged.
- Kogan L, Hellyer P, Downing R. The Use of Cannabidiol-Rich Hemp Oil Extract to Treat Canine Osteoarthritis-Related Pain: A Pilot Study. J Am Holist Vet Med Assoc. 2020;58:35–45. DOI 10.56641/UPRM3253. Our disclosure: HempMy Pet supplied the hemp extract and reimbursed clinic costs; per the journal we had no input into study design or interpretation.
If you find something here that conflicts with your veterinarian, email us at support@hempmypet.com and we will correct it.
These statements have not been evaluated by the Food and Drug Administration. Our products are not intended to diagnose, treat, cure, or prevent any disease. This article is educational and is not veterinary advice. Trazodone is a prescription medication — never start, stop, or change your dog's dose without your veterinarian.
