Trazodone is the drug you give before the thunderstorm, before the car ride, before the vet — so it is usually given in a hurry, by whichever adult is nearest the cupboard. The mistake has a shape: one person gives it on the way out of the door, the other gives it again by the car, and now there are two tablets in a dog about to be shut in a crate for the afternoon.
Search that and reassurance arrives fast. It's just a sedative. He'll sleep it off. Watch him a couple of hours. Most of those pages are question-and-answer threads, and their advice rests on two assumptions the veterinary literature does not support: that more trazodone means more sleep, and that two normal-looking hours settle it.
Key takeaways
- Don't give a second dose, and call rather than watch. VCA: "Do not give the pet two doses at once," and "if you suspect an overdose, or an adverse reaction to the medication, call your veterinary office immediately."¹
- A doubled dose is not twice the sedation. Merck: trazodone "selectively inhibits neuronal reuptake of serotonin at low doses and acts as an agonist at high doses," and "sedation usually occurs early in the course of toxicosis, followed by stimulatory signs."²
- The two-hour check lands in the wrong place. In six Beagles given oral trazodone, time to maximum plasma concentration averaged 445 ± 271 minutes — about 7.4 hours, with wide spread.³
- A second serotonergic drug is the thing to say on the phone. VCA: "when trazodone is used with other serotonergic drugs, serotonin syndrome is possible," listing SSRIs, tramadol and MAO inhibitors among those to use with caution.¹
Can I give my dog two doses of trazodone?
No. VCA's trazodone handout puts it in one line, immediately after its missed-dose advice: "Do not give the pet two doses at once."¹ That covers the deliberate version too — the storm is getting worse, the first tablet doesn't seem to have touched him, so surely one more would help.
If the second dose is already in, VCA's instruction for that moment is not to observe: "If you suspect an overdose, or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility."¹
None of this is a reason to panic. But it is also not a call to make from the sofa: what settles it — your dog's other medications, its heart and kidney status, how much drug is on board — is what a clinic has and a search result does not.
What should you do in the first hour?
Call, with four facts ready, and do not try to make the dog vomit on your own initiative. That window has usually closed: Merck sets the decontamination window for trazodone at "within 15–30 minutes" of ingestion, and only "if the patient is clinically normal".² By the time most owners notice and start reading, half an hour has gone.
What the clinic needs is arithmetic you can do faster than they can:
- Your dog's current weight, not last year's. Every threshold in this drug's literature is per kilogram.
- The tablet strength and how many went in. "Two tablets" means nothing without the number on them — count what is left against what was dispensed.
- The clock time of both doses. Not "this morning": the gap determines how much of the first was still present when the second arrived.
- Every other drug your dog is on, including supplements and anything from a different clinic. This is the question that changes the answer most often.
While you wait to be called back, put the dog somewhere quiet, enclosed and free of stairs, and stay with it; a sedated dog should not be near stairs. If you cannot reach a clinic, the ASPCA Animal Poison Control Center takes calls on (888) 426-4435, 24 hours a day, 365 days a year; a consultation fee applies.⁷
| Which situation are you in? | What it means | What to do |
|---|---|---|
| Two doses given close together by two people, otherwise healthy adult dog | The commonest version, and usually the least eventful — but the peak is still hours away³ | Call your clinic today. Don't give any further dose until they tell you to |
| You can't remember whether the first dose was given | Unknown — possibly a full dose already absorbed | Don't give another. Call and ask; uncertainty is not a reason to top up |
| Your dog is also on an SSRI, tramadol, an MAO inhibitor or another serotonergic drug | The interaction VCA singles out: "serotonin syndrome is possible"¹ | Call immediately and name every drug, including ones from other clinics |
| Doubling in a dog with severe heart disease, or liver or kidney impairment | The groups VCA flags for caution; VCA also notes effects "can be longer in pets with liver or kidney disease"¹ | Call immediately and say which condition — it changes the urgency |
| A chewed bottle, or a dose you cannot bound | Unbounded exposure — the amount is the whole question and you don't have it | Emergency. Clinic or ASPCA APCC (888) 426-4435 now⁷ |
| Agitation, tremors, a fever, or wild incoordination rather than sleepiness | Stimulatory signs, not sedation — see the serotonin syndrome criteria below² | Emergency — go in now |
From VCA Animal Hospitals' trazodone handout and the Merck Veterinary Manual. Every row ends in a phone call — they differ in how fast you dial, not whether.
Why isn't a double dose just twice the sleep?
Because trazodone does not do the same thing at every concentration. Merck's entry on the drug is one sentence that undoes most of what the forums assume: trazodone "selectively inhibits neuronal reuptake of serotonin at low doses and acts as an agonist at high doses."²
Those are two different pharmacological actions, not two intensities of one: at a therapeutic dose the drug dampens serotonin reuptake; push the concentration up and it starts stimulating serotonin receptors instead. Which is why Merck describes a real trazodone toxicosis as it does: "sedation usually occurs early in the course of toxicosis, followed by stimulatory signs."²
Read that sequence against how an owner spends the evening. The dog goes quiet, as expected. Then, hours later, it becomes restless, vocal, wobbly, wired — and the natural reading is that the drug is wearing off. The pharmacology says it may be the opposite: the second phase, arriving on schedule.
Two other sources point the same way. VCA's list of possible side effects includes "increased anxiety" and "aggression" alongside sedation and lethargy — the drug can go either way in an individual dog before any overdose is involved.¹ And in the Cornell study, when the same 8 mg/kg dose was given intravenously rather than orally, producing a far higher and faster peak, "all dogs immediately developed transient tachycardia" and "3 of 6 dogs developed aggression" — behaviour the authors called disinhibition.³ That was an intravenous dose in a controlled study, not a swallowed tablet, and it is not what two tablets will do to your dog. What it shows is the direction the drug moves as peak concentration climbs: not deeper into sleep.
When does trazodone actually peak, and how long should you watch?
Later than the number everyone repeats, and for much longer than two hours. The "one to two hours" figure is real but answers a different question. It comes from VCA, which says the medication "will take effect quickly, in about one to two hours, when used for short-term stress relief"¹ — that is when the calming becomes visible, not when the drug peaks in the blood.
For the second number there is exactly one published source in dogs. In 2013 a Cornell group gave six adult Beagles trazodone at 8 mg/kg by mouth and by vein in a crossover design. Orally, mean time to maximum plasma concentration was 445 ± 271 minutes — about 7.4 hours — with bioavailability of 84.6 ± 13.2%, so most of a swallowed tablet does arrive.³
The standard deviation is the part worth sitting with, and no competing page mentions it. A spread of ±271 minutes around a mean of 445 puts one standard deviation either side at roughly 3 hours to 12 hours. Six dogs of one breed, one dose, one set of conditions — and the moment the drug peaked varied across most of a working day. The authors said so themselves: there is "substantial variability in time to maximum plasma concentration," and "individualized approaches in dosing intervals may be necessary".³ Which is why "he was fine after two hours" is not the reassurance it sounds like: for many dogs, two hours is before the peak.
How long it lasts is more reassuring. VCA calls trazodone short-acting and says it "should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease."¹ Expect a long evening rather than a long week — but watch all of it, not the first two hours.
How do you tell an ordinary trazodone wobble from a real problem?
By what comes with it. Sedation and some unsteadiness are expected at a normal dose, and more common than owners realise. In a 2022 University of Wisconsin study, 32 healthy dogs had a full neurological examination before and 2.5 hours after a single ordinary dose. Seven — 22% — scored worse afterwards, showing "new or progressive" proprioceptive deficits: the paw-placement tests a neurologist uses to check a dog knows where its feet are.⁴ The authors' point was for vets — "ideally, trazodone should not be given before neurologic examination in dogs"⁴ — but it has a version for owners. About one dog in five scored worse on a neurologist's examination at a normal dose, so mild unsteadiness alone, in a dog otherwise calm and responsive, is the drug behaving as expected rather than the emergency.
What changes the picture is company. Merck defines serotonin syndrome as a cluster, not a single sign: "at least three of the following features: altered mental status, agitation, nervousness, myoclonus, hyperreflexia, tremors, diarrhea, incoordination, cardiovascular changes (heart rate and blood pressure), and fever."² Incoordination is on that list — but so are eight other things, and the combination is what matters. A wobbly, sleepy, responsive dog is a different animal from a wobbly, trembling, agitated, hot one. One further sign deserves naming because it frightens owners and rarely appears in general advice: VCA lists priapism — "persistent and painful erection of the penis" — among trazodone's side effects.¹ It is an adverse reaction, and VCA's instruction for any adverse reaction is to call immediately.¹
| What you're seeing | What it may point at | Urgency |
|---|---|---|
| Sleepy, unsteady, dilated pupils, but rousable and calm¹ | Expected drug effect; a normal dose alone does this to about one dog in five⁴ | Call the same day. Keep the dog confined and off stairs |
| Vomiting, gagging, diarrhoea¹ | Listed side effect — but also on the serotonin syndrome list² | Call now; say what else the dog takes |
| Agitation, tremors, muscle twitching, vocalising, pacing² | Stimulatory signs — Merck's "sedation early, then stimulatory signs" pattern² | Emergency — go in now |
| Three or more of: altered mental state, agitation, tremors, diarrhoea, incoordination, heart-rate change, fever² | Merck's own definition of serotonin syndrome | Emergency — go in now |
| Seizure, collapse, laboured breathing, disorientation¹ | On VCA's serotonin syndrome list | Emergency — go in now |
| Persistent, painful erection (priapism)¹ | Listed trazodone side effect¹ | Call now — VCA: call immediately for any adverse reaction¹ |
Signs as listed in VCA Animal Hospitals' trazodone handout and the Merck Veterinary Manual's antidepressant toxicoses chapter. This is a guide to urgency, not a diagnosis — describe what you are seeing to a veterinarian rather than matching it to a row yourself.
⚠️ When is this an emergency rather than a phone call?
When trazodone was not the only serotonergic drug in your dog — which is why the fourth question on the phone matters most.
VCA states it directly: "when trazodone is used with other serotonergic drugs, serotonin syndrome is possible," and lists among the drugs to use with caution alongside it "acepromazine, antihypertensive drugs, aspirin, azole antifungals, cisapride, CNS depressants, diuretics, fluoroquinolones, macrolide antibiotics, monoamine oxidase inhibitors, metoclopramide, NSAIDs, ondansetron, SSRI antidepressants, tramadol."¹ That list is not exotic. Fluoxetine for separation anxiety, tramadol for post-operative pain, ondansetron for nausea, an NSAID for arthritis — the same dog is very likely to be on one. Fluoxetine is the one most likely to be sitting alongside trazodone in a behaviour case, and it is also the one whose dosing is hardest to reconstruct afterwards, since a missed fluoxetine dose leaves no same-day sign and no blood level to check. Merck's account of how serotonin syndrome arises then reads almost like a description of the accident: it "often occurs because of repeated use or overdose of substances that result in increased free concentrations of serotonin."² A doubled dose is both at once.
VCA also names outright contraindications — trazodone "should NOT BE USED" in pets that "are using MAO (Monoamine oxidase) inhibitors" or "have angle-closure glaucoma" — and flags caution in dogs with "severe heart disease" or "liver or kidney impairment."¹ If your dog is in one of those groups, say so first.
Two findings are worth knowing, both measured at ordinary doses. A 2025 crossover trial in 20 healthy dogs found trazodone raised average and minimum heart rates and reduced heart rate variability, with no effect on the QT interval⁵ — so a sedated dog with a fast pulse is a documented pattern, not an automatic crisis. And a 2023 placebo-controlled study in 15 healthy dogs found platelet aggregation fell significantly on trazodone (95% to 62%, versus 95% to 91% on placebo), while bleeding time and platelet count were unchanged; the authors stressed "it is unknown if this represents a clinically relevant change."⁶ Trazodone is often prescribed for post-surgical confinement, so raise it with the surgeon if your dog has just had an operation.
What if you missed a dose instead of doubling it?
Then the stakes are lower, and VCA gives the fix: "If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once."¹
That last sentence does real work, because a missed dose is how most double doses begin: somebody remembers the tablet late and gives it, while the person who already gave it on time is in another room. And a missed dose never justifies catching up — if the reason for it has passed, the dose has missed its purpose, and giving it late adds risk without benefit. Ask your vet; it is a far calmer question than the other one.
How do you make sure this doesn't happen again?
By moving the record of the dose out of two people's heads and into one place both can see. Trazodone doublings have a recognisable anatomy, and it is almost never carelessness: the drug is given at unusual times, by whoever is available, mid-task — packing the car, closing the windows before a storm, getting the dog into a carrier. Each is a moment of divided attention with a second adult nearby.
What closes the gap:
- Log it as you give it, not afterwards. A record built from memory an hour later is a record of the thing that just failed.
- Write the strength and the count, not the drug. "Trazodone ✓" doesn't distinguish one 100 mg tablet from two 50 mg ones — the distinction the clinic will ask for.
- Assume the trigger prompted both of you. The cue that reminds you reminds your partner at the same moment, so a shared record beats a shouted "did you give him one?" — the failure in why pets miss medication doses, running in reverse.
- Keep situational drugs on the same list as daily ones. An occasional drug is the one nobody has a habit around, which is why it needs the written record more.
And if your dog takes both: trazodone and gabapentin are commonly given together before a stressful appointment — a 2025 study measured the pair, at 20 mg/kg gabapentin and 8 mg/kg trazodone, reducing the isoflurane requirement in anaesthetised dogs⁸ — so a household juggling two pre-visit sedatives has more chance of a mix-up. See a doubled gabapentin dose for that drug's version, how to avoid double dosing your pet's medication for the wider systems, and how to prepare for a vet visit for the rest.
Veterinary medical disclaimer: SteadyTails is a logging and coordination tool, not a substitute for veterinary care. Nothing here is a dosing instruction. Trazodone is prescribed off-label in dogs, tablet strengths vary, and the right dose is specific to your dog — only your veterinarian can tell you what to do about a doubled, missed or delayed dose. If your dog has received extra trazodone, or is agitated, trembling, feverish, vomiting, disoriented, badly uncoordinated or having a seizure, contact your veterinarian or an emergency animal hospital immediately. The ASPCA Animal Poison Control Center is available on (888) 426-4435, 24 hours a day, 365 days a year; a consultation fee may apply.⁷
The cupboard can't tell you whether anyone already used it
One tablet before the storm, two people, one anxious dog. SteadyTails records every dose with a name, a timestamp and the amount given, on a timeline the household can see — and clears the reminder on everyone's phone the moment somebody logs it. Coming soon to iOS and Android.
Join the SteadyTails waitlist →References
- VCA Animal Hospitals. Trazodone — "Trazodone is given orally (by mouth) in the form of a tablet. It may be given with food or on an empty stomach"; "This medication will take effect quickly, in about one to two hours, when used for short-term stress relief"; "If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once"; possible side effects "dilated pupils, sedation, lethargy, vomiting or gagging, colitis (inflammation of the colon), ataxia (loss of muscle control), priapism (persistent and painful erection of the penis), arrhythmias, increased anxiety, increased appetite, aggression"; "When trazodone is used with other serotonergic drugs, serotonin syndrome is possible"; "This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease"; should not be used in pets that "are using MAO (Monoamine oxidase) inhibitors" or "have angle-closure glaucoma", used with caution in pets that "have severe heart disease" or "have liver or kidney impairment"; drug interactions "acepromazine, antihypertensive drugs, aspirin, azole antifungals, cisapride, CNS depressants, diuretics, fluoroquinolones, macrolide antibiotics, monoamine oxidase inhibitors, metoclopramide, NSAIDs, ondansetron, SSRI antidepressants, tramadol"; "If you suspect an overdose, or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility." vcahospitals.com Retrieved 2026-08-29.
- Merck Veterinary Manual. Toxicoses in Animals From Human Antidepressants, Anxiolytics, and Sleep Aids — trazodone: "Selectively inhibits neuronal reuptake of serotonin at low doses and acts as an agonist at high doses. Shows some antagonism of alpha-1 adrenergic receptors. Sedation usually occurs early in the course of toxicosis, followed by stimulatory signs"; "An overdose of almost any antidepressant can result in GI signs, lethargy, ataxia, agitation, shaking, seizures, tachycardia or bradycardia, vocalization, and development of serotonin syndrome"; "If the patient is clinically normal, emesis should be induced if antidepressant ingestion happened recently — generally within 2 hours for venlafaxine and selective serotonin reuptake inhibitors (SSRIs); within 15–30 minutes for the tricyclic antidepressants mirtazapine, bupropion, and trazodone, and for the monoamine oxidase inhibitor selegiline"; "The group of clinical signs characterizing serotonin syndrome usually includes at least three of the following features: altered mental status, agitation, nervousness, myoclonus, hyperreflexia, tremors, diarrhea, incoordination, cardiovascular changes (heart rate and blood pressure), and fever"; "Serotonin syndrome often occurs because of repeated use or overdose of substances that result in increased free concentrations of serotonin, such as antidepressants or profound stimulants (eg, amphetamines)"; "Cyproheptadine is a serotonin antagonist often administered for treatment." merckvetmanual.com Retrieved 2026-08-29.
- Jay AR, Krotscheck U, Parsley E, et al. Pharmacokinetics, bioavailability, and hemodynamic effects of trazodone after intravenous and oral administration of a single dose to dogs. American Journal of Veterinary Research, 2013;74(11):1450–1456. "6 adult Beagles"; "Dogs received trazodone HCl (8 mg/kg) orally and IV in a randomized controlled crossover design"; "Following oral administration, the mean ± SD elimination half-life and absolute bioavailability were 166 ± 47 minutes and 84.6 ± 13.2%, respectively"; "Maximum plasma concentration following oral administration was 1.3 ± 0.5 μ/mL, and time to maximum plasma concentration was 445 ± 271 minutes"; "After IV administration, all dogs immediately developed transient tachycardia (184.3 ± 8.0 beats/min), and 3 of 6 dogs developed aggression"; "Results of this study indicated oral administration of trazodone resulted in acceptable absolute bioavailability, with substantial variability in time to maximum plasma concentration. Individualized approaches in dosing intervals may be necessary for dogs receiving oral trazodone. An orally administered dose of 8 mg/kg was well tolerated in dogs; IV administration of a dose of 8 mg/kg caused substantial adverse effects, including tachycardia and behavior disinhibition." PubMed Retrieved 2026-08-29.
- Lueck LC, Cameron S, Zidan N. Effects of trazodone administration on the neurologic examination in healthy dogs. Journal of Veterinary Internal Medicine, 2022;36(6):2142–2148. "Thirty-two healthy dogs between 1 and 6 years old"; "trazodone administration (6.25–8.60 mg/kg PO)"; "The sedation and anxiety assessments and neurologic examination were repeated 2.5 hours after trazodone administration"; "Seven of 32 (22%) dogs had worse scores on their neurologic examination after receiving trazodone, manifesting as new or progressive PR deficits"; "Although not clinically relevant, 18.7% of the dogs had consciousness levels that changed from bright, alert, responsive to quiet, alert, responsive after trazodone administration"; "Ideally, trazodone should not be given before neurologic examination in dogs." PubMed (free full text) Retrieved 2026-08-29.
- Silvia VT, DeFrancesco TC, Love KR, Tou SP, Keene BW. Effect of trazodone on heart rate, heart rate variability, and QT-intervals in dogs. Journal of Veterinary Cardiology, 2025;61:20–28. "Twenty healthy adult client-owned dogs"; "Dogs received trazodone (6 mg/kg q 8 h) or placebo for 24 h, during which a 24-h ambulatory electrocardiogram (ECG) (Holter) was recorded"; "Dogs receiving trazodone had higher average HRs (P=0.035), higher minimum HRs (P<0.001), and reduced HR variability parameters (P<0.001) on the Holter recordings. Electrocardiogram-derived QT interval was not different between groups"; "Trazodone increased HR and decreased HRV. Possible explanations include a previously described anticholinergic effect or a possible decrease in blood pressure causing a reflex response. No demonstrable effect on QTi was identified in this cohort of healthy dogs using standard trazodone dosing." PubMed Retrieved 2026-08-29.
- Benjamin EJ, Nelson OL, Baumwart R, Haines J. Adverse effects of trazodone in dogs on primary hemostasis and electrocardiogram: A single-blinded placebo-controlled crossover study. Journal of Veterinary Internal Medicine, 2023;37(6):2131–2136. "Fifteen apparently healthy, client-owned dogs"; "Dogs were administered trazodone (5 to 7.5 mg/kg PO Q12h) or placebo"; "No significant difference was detected in the BMBT, PFA-100 closure times, platelet counts, and cQT interval between trazodone or placebo. However, using Plateletworks, there was a significant decrease in platelet aggregation after administration of trazodone (95%; 81-97 vs 62%; 39-89, P = .002) and not placebo (95%; 81-97 vs 91%; 81-96, P = .21)"; "It is unknown if this represents a clinically relevant change or if dogs with preexisting impairment in primary hemostasis or receiving higher dosages or longer durations of trazodone could have a more substantial change in hemostatic variables." PubMed (free full text) Retrieved 2026-08-29.
- ASPCA. Animal Poison Control Center — "Call Now: (888) 426-4435"; "We are available 24/7, 365 days a year"; "ASPCA Poison Control is your best resource for any animal poison-related emergency, 24 hours a day, 365 days a year"; "A consultation fee may apply." aspca.org Retrieved 2026-08-29.
- Aiello J, Carson B, Aarnes T, Wanstrath A, McLoughlin M. Effect of oral premedication with gabapentin and trazodone combination on the MAC of isoflurane in dogs. American Journal of Veterinary Research, 2025;86(3):ajvr.24.09.0254. "To determine the effect of the administration of oral gabapentin (20 mg/kg) and trazodone (8 mg/kg) on the MAC of isoflurane in dogs"; "The mean ± SD MAC of isoflurane in dogs was significantly lower with gabapentin and trazodone premedication and isoflurane (0.625 ± 0.18%) compared with isoflurane alone (0.95 ± 0.14%)"; "Oral premedication with gabapentin and trazodone could be administered before anesthesia to decrease MAC, thus limiting dose-dependent anesthetic risks." PubMed Retrieved 2026-08-29.