Trazodone for Dogs: Side Effects

Anxiety affects roughly 44% of dogs at some point in their lives, according to researchers in the Journal of Veterinary Behavior — making it one of the most common behavioral health concerns in canines. Trazodone (brand names Desyrel® and Oleptro®) is a prescription human antidepressant that has become one of the most widely used anxiety medications in veterinary medicine. While it is not FDA-approved for veterinary use, veterinarians can legally prescribe it for dogs under “extra-label” or “off-label” use provisions. Studies show 80% of dogs taking trazodone experience no negative side effects (Veterinary Information Network data, confirmed by Small Door Veterinary). However, understanding every possible reaction — and when to call the vet — is critical for every dog owner whose pet takes this medication.

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  What are the most common side effects of trazodone in dogs? The most common side effects are sedation and mild digestive upset. PetMD (September 2025) confirms: “The biggest side effect of trazodone is digestive upset (vomiting, diarrhea, nausea).” Small Door Veterinary reports the most common effects from ASPCA data were sedation/lethargy (43% of affected dogs), ataxia/unsteady gait (16%), and vomiting (14%). Mild drowsiness and a “drugged” or quiet appearance are expected effects — not a cause for alarm — and typically lessen as the dog develops tolerance.

  The ASPCA Animal Poison Control Center analyzed 417 trazodone exposures in 379 dogs (2009–2013), providing the most comprehensive real-world safety data. In 104 dogs that experienced any adverse effects: sedation and lethargy were the most common (43%), followed by ataxia/unsteady walking (16%) and vomiting (14%). Importantly, Small Door Veterinary confirms that 80% of dogs on trazodone experience no negative side effects according to Veterinary Information Network data. The PMC/NCSU peer-reviewed clinical trial (North Carolina State University College of Veterinary Medicine) found trazodone was well-tolerated at all dosages tested, with no adverse effects requiring medical treatment, dosage adjustment, or drug withdrawal. The most common observation was transient “drugged” affect — temporary quietness that resolved on its own. If your dog seems unusually calm or slightly groggy, this is typically the intended effect working, not a dangerous reaction.
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  Why is my dog shaking after trazodone? Mild shaking or trembling can occur as a side effect of trazodone — especially at higher doses or in dogs who are more sensitive to the medication. If the shaking is mild and your dog is otherwise alert, contact your vet for guidance. However, if shaking is accompanied by severe agitation, high fever, rapid heart rate, vomiting, dilated pupils, or seizures, this may indicate serotonin syndrome — a medical emergency requiring immediate veterinary care. Call your vet or an animal poison control center without delay if multiple symptoms are present together.

  Drugs Naturally Magazine documents tremors and seizures as possible trazodone side effects, attributed to the drug’s influence on serotonin levels affecting neurons. ASPCA Pro’s clinical toxicology data confirms that signs of trazodone overdose/toxicosis include seizures and tremors (alongside ataxia, hypotension, disorientation, and urinary incontinence). TotalVet notes: “the most severe possible side effect of trazodone use is serotonin syndrome” — which can cause trembling/shaking, confusion, increased heart rate, diarrhea, fever, and seizures. VCA Hospitals confirms the short-acting nature: effects should resolve within 24 hours in healthy dogs (longer in pets with liver or kidney disease). If shaking starts within 30–60 minutes of a dose and is isolated without other symptoms, it may be the drug taking effect on a sensitive dog. ASPCA Pro notes signs most often appear within 30–60 minutes of exposure. Reduce dose by half on the next administration and contact your vet.
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  Why is my dog panting after taking trazodone? Panting after trazodone is a documented, moderately common side effect. Remedy Veterinary Specialists confirm: “Some pets may show increased agitation or hyperactivity, including frantic whining and panting. This is more likely at higher doses or when combined with other medications such as sedatives or pain relievers.” If the panting is mild and your dog is calm overall, monitor them and inform your vet at the next visit. If panting is severe, rapid, accompanied by restlessness, high heart rate, or other distress signs, contact your vet the same day — this may represent paradoxical excitation or early serotonin syndrome.

  Today’s Veterinary Nurse (ASPCA data) confirms panting as one of the adverse behavioral events associated with trazodone use. Dr. Buzby’s ToeGrips (February 2025) documents owner-reported cases: “Even when it is not warm out, or your dog hasn’t recently exercised, he or she may still be panting. Sometimes he or she might also be panting and pacing.” This reflects the paradoxical excitation effect that can occur — some dogs experience the opposite of sedation, becoming more agitated. VCA Hospitals’ clinical reference confirms panting as a documented possible side effect. Adjust timing: if panting occurs consistently, discuss with your vet whether giving trazodone with food (vs. on an empty stomach), adjusting the dose downward, or switching the time of administration (morning vs. evening) might reduce this response. Do not abruptly stop daily trazodone without vet guidance.
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  Why is my dog vomiting after trazodone? Vomiting is the most commonly reported non-sedation side effect of trazodone in dogs. PetMD names it as the “biggest side effect.” GoodRx advises: “If your dog gets an upset stomach when they take trazodone, give each tablet with a small meal or treat.” This simple change resolves gastrointestinal upset for most dogs. VCA Hospitals confirms: “If your pet vomits or acts sick after receiving the medication on an empty stomach, try giving the next dose with food or a small treat.” One or two vomiting episodes after starting trazodone are common; repeated or severe vomiting warrants a call to your vet.

  Vomiting was reported in 14% of affected dogs in ASPCA’s analysis. Drugs.com (medically reviewed) confirms gastrointestinal upset including nausea, vomiting, diarrhea, and constipation as documented trazodone side effects due to disruption of gut motility from serotonergic effects on the gastrointestinal tract. Dogs Naturally Magazine specifically identifies colitis (colon inflammation) as a possible trazodone effect, with symptoms including diarrhea, vomiting, weight loss, and abdominal pain. PetPlace confirms: “Most side effects are mild and improve within a few days.” The standard veterinary guidance is clear: giving trazodone with a small amount of food is the simplest and most effective solution for stomach-related side effects. Always use a small treat or partial meal — not a full meal — as a full meal may delay the drug’s absorption and reduce its effectiveness for anxiety control.
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  Is it bad to give a dog trazodone every day? Daily trazodone is commonly prescribed and generally safe for most dogs when monitored by a veterinarian. The PMC/NCSU peer-reviewed clinical trial found trazodone was well-tolerated at all dosages with no adverse effects requiring treatment or withdrawal. SingleCare (updated March 16, 2026, medically reviewed by Emma Ryan, DVM) notes trazodone “may also be an option for age-related anxiety, which can develop as the pet loses memory and cognitive function.” Dogs on daily trazodone do not develop dependency in the same way as benzodiazepines, but gradual tapering off (not abrupt stopping) is recommended if discontinuing after long-term use. Dogs with heart disease, liver disease, or kidney disease require extra monitoring.

  Dr. Buzby’s ToeGrips (February 2025) documents veterinary guidance: “Both of these medications can be given long term and I have patients that take them every day.” VCA Hospitals confirms: “No specific monitoring is needed while your pet is taking this medication” — though the veterinarian may monitor for effectiveness. SingleCare (March 2026) notes separation anxiety dogs may take trazodone “when the dog is home alone during the day” as a long-term treatment approach. The ASPCA’s guidance through veterinary channels confirms there is tolerance with trazodone — dogs that build tolerance may require gradually increasing doses. PetPlace advises: “Don’t stop abruptly — if your pet has been on trazodone long-term, tapering off slowly may be necessary.” For senior dogs: SingleCare specifically warns to “seek medical advice at a vet visit before giving trazodone or other medications to senior dogs” to avoid adverse effects including liver damage, as older dogs metabolize medications differently.
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  What is the biggest side effect of trazodone? PetMD (September 2025) is direct: “The biggest side effect of trazodone is digestive upset (vomiting, diarrhea, nausea).” The most serious possible side effect — though rare — is serotonin syndrome: a potentially life-threatening buildup of serotonin in the brain that can cause seizures, hyperthermia, severe trembling, extreme agitation, rapid heart rate, and in severe cases, coma and death. Serotonin syndrome is most likely when trazodone is combined with other serotonergic drugs (such as tramadol, fluoxetine, amitriptyline) or in cases of overdose.

  TotalVet summarizes clearly: “Serotonin syndrome can culminate in a coma and, depending on the severity of the situation, even have fatal consequences. Therefore, a dog with serotonin syndrome is considered to be a medical emergency.” Small Door Veterinary documents that serotonin syndrome typically develops within one to twelve hours after taking the medication. MedVet confirms: “Signs of serotonin syndrome include confusion, increased heart rate, shivering, diarrhea, fever, and seizures.” Today’s Veterinary Nurse (from ASPCA data) provides the clinical frequency ranking of serotonin syndrome signs in dogs, in order from most to least common: vomiting, diarrhea, seizures, hyperthermia (high fever), hyperesthesia (extreme sensitivity to touch), depression, mydriasis (dilated pupils), vocalization, death, blindness, hypersalivation, dyspnea (difficulty breathing), ataxia/paresis, disorientation, hyperreflexia (exaggerated reflexes), and coma. Treatment: cyproheptadine (a serotonin antagonist) is the standard treatment for serotonin syndrome in dogs; phenothiazines are used cautiously due to hypotensive effects.
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  How long do trazodone effects last in a dog? When used for situational anxiety: trazodone begins working in 30 minutes to 2 hours and lasts 6–12 hours in healthy dogs (PetMD: “Trazodone generally lasts about eight to twelve hours in dogs”). When used for long-term anxiety treatment: full behavioral improvement may take 2–4 weeks of daily dosing before the complete effects are seen. Duration is longer in dogs with liver or kidney disease — these dogs clear the medication more slowly, so effects can persist beyond 12 hours. VCA Hospitals confirms: “This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.”

  GoodRx (June 2025) confirms: trazodone takes “1 to 3 hours to start working in dogs. It typically lasts 6 to 12 hours in healthy dogs and longer in animals with liver or kidney disease.” SingleCare (March 2026): “Trazodone works quickly — usually within 30 minutes to an hour.” PetMD confirms: “When used only as needed, trazodone will typically take effect in one to two hours. When used daily, improvement in your pet’s behavioral condition may take a few weeks.” For situational use (vet visits, fireworks): give at least 90 minutes before the stressful event (PetMD), or 1–2 hours before (TotalVet). Mixlab (February 2026) confirms: “After administration, the medication usually begins working in 30 minutes to an hour. It can provide relief between three and 12 hours once a dog takes the medication.” Any side effects from a dose should also resolve within this 6–12 hour window. If side effects persist beyond 24 hours, contact your veterinarian.
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  Is trazodone really safe for dogs? Yes, for most healthy adult dogs under veterinary supervision — with specific cautions. The peer-reviewed PMC/NCSU clinical study found “no adverse effects that required medical treatment, dosage adjustment, or withdrawal of trazodone” at standard doses. 80% of dogs experience no negative effects. However, trazodone should be used with caution or avoided entirely in dogs with: severe heart disease, significant liver disease, kidney failure, angle-closure glaucoma, and dogs taking MAO inhibitors (such as selegiline). Never share a human’s trazodone prescription with a dog — always get a separate veterinary prescription and dose.

  PetMD confirms trazodone’s legal status: “While trazodone is FDA-approved for human use, it is currently not FDA-approved as a veterinary medication. It is, however, readily utilized in the veterinary field, and veterinarians can legally prescribe certain human drugs in animals in certain circumstances.” Small Door Veterinary notes: “The safety profile of trazodone in dogs is well established.” Dogs Naturally Magazine confirms a 2016 Ohio State University College of Veterinary Medicine study of 120 dogs found trazodone reduced signs of stress in hospitalized patients. Small Door confirms trazodone is contraindicated (should not be used) in: dogs hypersensitive to trazodone, dogs on MAO inhibitors (selegiline), dogs with angle-closure glaucoma, or dogs in liver, heart, or kidney failure. The human prescription issue: GoodRx explicitly warns: “Trazodone for dogs is the same medication that humans use. But you shouldn’t give your dog a prescription that was filled for you. Only give your dog medications prescribed by your veterinarian” — different dosing applies and human prescriptions may contain inactive ingredients harmful to dogs.
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  What drugs interact dangerously with trazodone in dogs? Highest-risk combinations (serotonin syndrome risk): tramadol (very common combination — used for pain after surgery; significantly increases serotonin syndrome risk), fluoxetine (Prozac), amitriptyline, clomipramine, mirtazapine, metoclopramide, ondansetron, MAO inhibitors (selegiline — used for Cushing’s disease and canine cognitive dysfunction). Also use caution with: benzodiazepines (alprazolam, diazepam) — may cause excessive sedation; NSAIDs — increased bleeding risk; digoxin — heart rhythm effects; diuretics — altered drug levels. Always tell your vet every medication, supplement, and herbal remedy your dog takes.

  MedVet (reviewed by Emily Klosterman, DVM, MS, DACVIM) provides the most complete drug interaction list: tramadol (pain medication) — serotonin syndrome; mirtazapine (appetite stimulant) — serotonin syndrome; metoclopramide (anti-nausea) — serotonin syndrome; ondansetron (anti-nausea, chemotherapy dogs) — serotonin syndrome. Small Door Veterinary adds: some drug interactions may cause excessive sedation; others increase bleeding risk; others cause heart rhythm problems. Today’s Veterinary Nurse (from veterinary toxicology data) confirms “trazodone interacts with numerous drugs, and some of these interactions may have clinically significant effects.” ASPCA Pro specifically highlights the trazodone + tramadol combination as a particular concern for serotonin syndrome — a combination frequently prescribed in post-surgical recovery when both drugs are used simultaneously. VCA Hospitals gives the most practical advice: “Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.” Herbal serotonin-affecting supplements (St. John’s Wort, 5-HTP) must be disclosed even if not prescription drugs.
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  What is the correct trazodone dosage for dogs, and what if I missed a dose? Standard dosage: 1–3 mg per pound of body weight (approximately 2.5–15 mg/kg), given every 8–24 hours depending on use. Tablets are available in 50 mg, 100 mg, 150 mg, and 300 mg. Only use immediate-release tablets — extended-release tablets are not appropriate for dogs. Missed dose: give as soon as remembered, but if the next dose is close (within a few hours), skip the missed dose and resume normal schedule. Never double-dose. Never adjust the dose on your own without veterinary guidance — the dose range is wide and overdose is possible.

  SingleCare (medically reviewed, March 16, 2026): “The dosage for trazodone is typically 1–3 mg per pound of body weight.” Drugs.com: “The standard dosage for dogs is 1.7 to 19.5 mg/kg/d on a daily or as-needed basis with immediate action (not extended-release) tablets.” TotalVet confirms tablets are available in 50 mg, 100 mg, 150 mg, and 300 mg — and scored in the middle to allow splitting for smaller doses. PetPlace dosage by weight (general guideline): 10-lb dog: starting at 25–30 mg; 25-lb dog: 25–75 mg; 50-lb dog: 50–150 mg; 75-lb dog: 75–225 mg; 100-lb dog: 100–300 mg — always follow your veterinarian’s exact instructions over these general ranges. ASPCA Pro: “At ASPCA Poison Control, we become concerned with naïve dogs who are exposed to trazodone at 5 mg/kg, though mild signs can be seen at doses lower than that.” Meaning a dog not used to the medication is more sensitive to toxicity than one who has been taking it regularly — this is why starting low and titrating up slowly is essential.

Sources: PetMD petmd.com Sep 2025 (biggest side effect digestive upset vomiting diarrhea nausea; serotonin syndrome immediate care; off-label/extra-label FDA; 90 min before event; 8–12 hrs duration; 68–77°F storage; serotonin syndrome signs; compounded available; not in hypersensitive/heart/liver/kidney failure/glaucoma/MAOI); VCA Hospitals vcahospitals.com (short-acting 24hr; longer liver kidney disease; off-label; empty stomach/food; do not double-dose; SARI class; serotonin syndrome signs; drug interactions; storage 20–25°C); Small Door Veterinary smalldoorvet.com (44% dogs anxiety J Vet Behavior; 80% no negative effects Vet Info Network; sedation lethargy 43% ataxia 16% vomiting 14% ASPCA data; contraindications hypersensitive MAOI glaucoma heart/liver/kidney failure; drug interactions sedation bleeding heart rhythm; serotonin syndrome 1–12 hrs after dose; incoordination vomiting diarrhea agitation dilated pupils drooling increased heart rate panting); SingleCare singlecare.com Mar 16 2026 medically reviewed Emma Ryan DVM (1–3mg/lb dosage; 50/100/150/300mg tablets; 1–2hr before stressful event; every 6/8/24hr for ongoing; separation anxiety daily; age-related anxiety senior dogs monitor; ASPCA titrate slowly; do not exceed max); PMC/NCSU pmc.ncbi.nlm.nih.gov (peer-reviewed clinical trial NCSU CVM; well-tolerated all dosages; no adverse effects requiring treatment dosage adjustment withdrawal; transient drugged affect; no ataxia disorientation stumbling oral administration; cardiac function well-preserved vs imipramine; 3.5–10mg/kg doses studied); ASPCA Pro aspcapro.org (417 exposures 379 dogs 2009–2013; signs 30–60min; 10–12hrs duration; ataxia hypotension hypertension bradycardia tachycardia disorientation hyperesthesia urinary incontinence apnea seizures tremors; 5mg/kg concern naive dogs; IV fluids symptomatic treatment; emesis 1hr; cyproheptadine serotonin syndrome; diazepam tremors seizures); Today’s Veterinary Nurse todaysveterinarynurse.com ASPCA data (drugged behavior drowsiness panting anxiety/agitation vomiting counter-surfing excitation sedation hunger colitis aggression; serotonin syndrome signs order vomiting diarrhea seizures hyperthermia hyperesthesia depression mydriasis vocalization death blindness hypersalivation dyspnea ataxia disorientation hyperreflexia coma; cyproheptadine treatment; trazodone+tramadol interaction); GoodRx goodrx.com Jun 2025 (1–3hrs onset 6–12hrs healthy dogs; give with food if upset stomach; do not share human prescription; gabapentin combination possible; not for pain; lower dose to start); Drugs.com drugs.com (1.7–19.5mg/kg/d; SARI class; within 30min–1hr onset 3–12hr effects; paradoxical hyperactivity; liver damage rare; start low increase 3–5 days; extended-release not appropriate); MedVet medvet.com reviewed Emily Klosterman DVM MS DACVIM (SAIM) (tramadol mirtazapine metoclopramide ondansetron interactions serotonin; cardiac arrhythmias allergic reactions; not for severe heart disease liver kidney; acupuncture massage integrative alternatives); TotalVet total.vet (serotonin syndrome coma fatal; MAOI interaction; overdose IV fluids symptomatic; test before needed event; 1–2hr before stressful event; 50/100/150/300mg tablets); Remedy Veterinary Specialists remedyvets.com (frantic whining panting agitation higher doses + other medications; serotonin syndrome symptoms GI seizures dilated pupils disorientation drooling); Dr. Buzby’s ToeGrips toegrips.com Feb 2025 (panting/pacing; urinary incontinence reports; long-term daily use documented; ASPCA Pet Poison Helpline 855-764-7661); PetPlace petplace.com (2.5–15mg/lb every 8–24hr avg starting 3.5mg/lb; taper off long-term; behavior plan with medication; disclose full history; overdose emergency vet)

Sources: Small Door Veterinary (80% no negative effects; Vet Info Network); ASPCA Animal Poison Control 2009–2013 (sedation 43% ataxia 16% vomiting 14%); PetMD Sep 2025 (8–12hr duration); GoodRx Jun 2025 (1–3hr onset; 6–12hr healthy dogs); SingleCare Mar 2026 (1–3mg/lb); ASPCA Pro (serotonin syndrome 30–60min onset; 5mg/kg concern); Small Door Veterinary (serotonin syndrome 1–12hr after dose)

Side effects are organized by urgency. Blue = common and usually mild. Amber = moderate — inform your vet at the next visit or sooner. Red = serious — contact your vet or animal poison control immediately.

Sources: PMC/NCSU pmc.ncbi.nlm.nih.gov (transient drugged affect no motor impairment oral doses; no adverse events requiring treatment withdrawal); Small Door Veterinary (sedation 43% ataxia 16% vomiting 14% ASPCA data; 80% no effects); ASPCA Pro aspcapro.org (serotonin syndrome signs order; urinary incontinence overdose; 5mg/kg naive dogs; cyproheptadine treatment; IV fluids); PetMD Sep 2025 (biggest side effect digestive upset; serotonin syndrome seek immediate care; 8–12hr duration); GoodRx Jun 2025 (give with food if stomach upset); Today’s Veterinary Nurse todaysveterinarynurse.com (drugged drowsiness panting vomiting counter-surfing trash-raiding agitation colitis aggression; serotonin syndrome order of signs); Drugs.com drugs.com (paradoxical hyperactivity disinhibition; colitis; arrhythmia); MedVet medvet.com (arrhythmias allergic reactions rare; increased anxiety possible; tramadol mirtazapine metoclopramide ondansetron interactions); Remedy Veterinary Specialists remedyvets.com (frantic whining panting agitation higher doses + combinations; increased appetite); Dogs Naturally Magazine dogsnaturallymagazine.com (tremors seizures; colitis; arrhythmia cardiac ion channels; aggression); Dr. Buzby’s ToeGrips toegrips.com (urinary incontinence owner reports; dose reduction resolved; panting pacing; ataxia IV vs oral study)

Frequency: Situational use (vet visits, fireworks) — single dose 90 min to 2 hours before event. Daily use — every 8, 12, or 24 hours depending on condition. Storage: 68–77°F (20–25°C) in an airtight, light-protected container. Keep out of reach of children and other pets.

Sources: SingleCare Mar 2026 (1–3mg/lb; 50/100/150/300mg tablets); Drugs.com (1.7–19.5mg/kg; immediate-release only); PetMD (90min before event; follow vet label); TotalVet (50/100/150/300mg available; increase 3–5 days); ASPCA Pro (5mg/kg concern naive dogs; 30–60min onset); PetPlace (2.5–15mg/lb dosage range; do not double-dose)

Sources: MedVet (tramadol mirtazapine metoclopramide ondansetron interactions; serotonin syndrome; cardiac arrhythmias); Small Door Veterinary (drug interactions: sedation bleeding heart rhythm; MAOI contraindicated); VCA Hospitals (disclose all meds vitamins supplements herbal therapies); TotalVet (SSRI fluoxetine interaction; MAOI interaction); Today’s Veterinary Nurse (trazodone+tramadol specific concern; cyproheptadine treatment serotonin syndrome)

Sources: PMC/NCSU (well-tolerated all dosages; no treatment required; no withdrawal); Small Door Veterinary (80% no effects; safety profile well established; contraindications); PetMD Sep 2025 (biggest side effect digestive upset; 8–12hr duration; vomiting diarrhea nausea; serotonin syndrome immediate emergency care); VCA Hospitals (within 24hr stops; longer liver kidney disease); GoodRx Jun 2025 (give with food; 6–12hr healthy dogs); Dr. Buzby’s ToeGrips Feb 2025 (long-term daily patients vet-confirmed); SingleCare Mar 2026 medically reviewed Emma Ryan DVM (age-related anxiety senior dogs; daily separation anxiety; titrate slowly; taper not stop abruptly); ASPCA Pro (serotonin syndrome order vomiting diarrhea seizures hyperthermia; cyproheptadine; 888-426-4435); TotalVet (1–2hr before event; serotonin syndrome coma fatal; MAOI contraindicated)

Always work with your licensed veterinarian when using trazodone. The buttons below link to official veterinary and clinical resources. Never adjust your dog’s trazodone dose without speaking to your vet first.