This page focuses on urgent assessment. Routine wellness exams, preventive care, and monitoring of stable conditions are provided through scheduled general wellness appointments.
Antidepressant Toxicity in Dogs & Cats
Antidepressant toxicity in dogs and cats can range from mild behavioral changes to life-threatening neurologic and cardiovascular complications, depending on the drug, dose, formulation, and individual sensitivity.
This includes exposure to human antidepressants, anti-anxiety medications, sedatives, and mood-stabilizing drugs, and may also be searched as SSRI toxicity, antidepressant overdose, serotonin syndrome, psych med ingestion, or anxiety medication poisoning in pets.
Definition
Antidepressant toxicity is a clinical toxic exposure, not a diagnosis. It occurs when a dog or cat ingests or is exposed to medications that alter brain neurotransmitters such as serotonin, norepinephrine, or dopamine.
These drugs can overstimulate the central nervous system and cardiovascular system, sometimes causing serotonin syndrome, seizures, abnormal heart rhythms, or dangerous changes in body temperature.
Both human-labeled and veterinary-labeled medications can cause toxicity, and clinical severity cannot be determined by dose alone.
Locally and globally, antidepressant and anti-anxiety exposures are increasing as these medications become more common in households with pets.
Who This Page Is For
• Dogs or cats that may have ingested human antidepressants, anxiety medications, or sedatives
• Pets with sudden agitation, restlessness, tremors, weakness, collapse, or seizures
• Dogs or cats with vomiting, hypersalivation, dilated pupils, or abnormal behavior
• Pets exposed to pill bottles, weekly pill organizers, purses, backpacks, or dropped medications
• Any pet acting “off,” hyper-sensitive, unusually quiet, or suddenly aggressive after possible medication exposure
The following human medications are commonly involved in antidepressant toxicity cases in dogs and cats.
Presence of any of these in the home increases risk if accessed by pets.
Selective serotonin reuptake inhibitors (SSRIs):
• Fluoxetine (Prozac)
• Sertraline (Zoloft)
• Paroxetine (Paxil)
• Citalopram (Celexa)
• Escitalopram (Lexapro)
• Fluvoxamine (Luvox)
Serotonin–norepinephrine reuptake inhibitors (SNRIs):
• Venlafaxine (Effexor)
• Desvenlafaxine (Pristiq)
• Duloxetine (Cymbalta)
• Milnacipran
• Levomilnacipran
Tricyclic antidepressants (TCAs):
• Amitriptyline
• Clomipramine
• Imipramine
• Doxepin
• Nortriptyline
Atypical antidepressants / anti-anxiety medications:
• Bupropion (Wellbutrin)
• Mirtazapine
• Trazodone
• Vortioxetine
• Nefazodone
Monoamine oxidase inhibitors (MAOIs):
• Selegiline
• Phenelzine
• Tranylcypromine
Atypical antipsychotics and mood stabilizers:
• Quetiapine (Seroquel)
• Risperidone
• Olanzapine
• Aripiprazole
• Clozapine
Combination products and related agents:
• Fluoxetine + Olanzapine combinations
• Weight-loss or smoking-cessation medications containing antidepressants
Who This Page Is Not For
• A pet that briefly sniffed a closed pill bottle without access to medication.
If you are unsure whether an exposure is significant, that uncertainty itself warrants veterinary assessment.
Related Urgent Symptoms
• Toxin Exposure In Dogs And Cats
• Serotonin Syndrome
• Seizures or Convulsions
• Dog Lethargic and Weak
• Cat Lethargic and Weak
• Vomiting And Diarrhea
• Sudden Collapse (Syncope)
• Pale Gums (Emergency)
What This Can Look Like at Home
Owners may notice subtle or sudden changes, including:
• Restlessness, pacing, whining, or agitation
• Lethargy, weakness, or difficulty standing
• Trembling, muscle stiffness, or twitching
• Vomiting, drooling, or gagging
• Dilated pupils or unusual eye movements
• Sudden behavioral changes such as fear, aggression, or confusion
Some pets appear normal at first, then worsen hours later as the drug is absorbed.
Why This Can Be Hard to Judge
Clinical signs do not reliably match the amount ingested. A small dose can cause serious effects in some pets, while others appear mildly affected at first.
Extended-release medications can delay symptoms, leading to a false sense of safety.
Pets often mask neurologic or internal distress, and early signs may be mistaken for anxiety, excitement, or fatigue.
Cats, in particular, may appear quiet or withdrawn despite significant toxicity.
The Improvement Trap
Temporary improvement does not equal resolution.
Some dogs and cats appear calmer or less symptomatic after initial agitation, only to develop tremors, seizures, heart rhythm changes, or hyperthermia hours later.
Symptoms may cycle or escalate, especially with sustained-release antidepressants or combination medications.
Waiting for symptoms to “pass” can delay care during the most critical treatment window.
What Is Easy to Miss at Home
When This Can Be an Emergency
Any Antidepressant toxicity should be treated as urgent because serious complications can develop quickly or be delayed.
Seek same-day urgent care immediately if any of the following are present:
• Seizures, collapse, or uncontrolled tremors
• Marked agitation, confusion, or abnormal aggression
• Weakness, inability to stand, or sudden lethargy
• Very high or very low heart rate, irregular heartbeat, or collapse
• Rapid breathing, panting, or difficulty breathing
• High body temperature or hot ears/paws
• Repeated vomiting, drooling, or inability to keep food down
• Known or suspected ingestion of extended-release medications
• Exposure in cats, small dogs, seniors, or pets with heart, liver, or seizure conditions
This is a decision-pivot condition where delay can increase risk.
How Veterinarians Assess This
Clinical signs alone cannot reliably determine severity.
Symptoms can appear similar while representing very different internal disease processes. Diagnostic testing is how veterinarians determine whether a condition is mild and self-limiting or serious and potentially life-threatening, and how they guide appropriate care.
Diagnostic testing may include:
• Complete blood count (CBC) to evaluate systemic stress, infection, or complications
• Serum chemistry profile to assess liver, kidney, electrolyte, and metabolic effects
• Blood glucose testing to detect hypo- or hyperglycemia
• Electrolyte evaluation (especially sodium and potassium)
• Urinalysis to assess kidney function and hydration
• Electrocardiogram (ECG) to identify arrhythmias or conduction abnormalities
• Blood pressure monitoring to detect hypertension or hypotension
Additional disease-specific testing (such as drug screening, coagulation testing, or advanced cardiac monitoring) may be considered based on the overall clinical picture.
Diagnostic testing is what determines severity and guides appropriate care.
Veterinary Differentials - Serious / Must-Rule-Out First
• Antidepressant toxicity – Exposure to medications that alter brain neurotransmitters, potentially causing neurologic and cardiac instability.
Tests may include CBC, serum chemistry profile, electrolyte testing, ECG, blood glucose testing.
• Serotonin syndrome – Excess serotonin activity leading to agitation, tremors, hyperthermia, and neurologic dysfunction.
Tests may include CBC, serum chemistry profile, electrolyte testing, blood glucose testing, temperature monitoring.
• Seizure disorder – Primary or secondary neurologic disease causing convulsions or collapse.
Tests may include CBC, serum chemistry profile, blood glucose testing, electrolyte testing.
• Cardiac arrhythmia – Abnormal heart rhythm causing weakness, collapse, or sudden death.
Tests may include ECG, blood pressure measurement, serum chemistry profile.
• Heatstroke – Dangerous elevation of body temperature that may mimic drug toxicity.
Tests may include CBC, serum chemistry profile, coagulation testing, electrolyte testing.
• Other toxin ingestion – Exposure to non-antidepressant toxic substances with overlapping signs.
Tests may include CBC, serum chemistry profile, electrolyte testing, urinalysis.
Veterinary Differentials - Common / More Typical
• Sedative or anti-anxiety medication exposure – Ingestion of medications that depress or dysregulate the nervous system.
Tests may include CBC, serum chemistry profile, blood glucose testing.
• Gastrointestinal irritation or gastritis – Medication-related stomach upset causing vomiting or drooling.
Tests may include serum chemistry profile, electrolyte testing.
• Hypoglycemia – Low blood sugar leading to weakness, tremors, or collapse.
Tests may include blood glucose testing, serum chemistry profile.
• Electrolyte imbalance – Altered sodium or potassium affecting neurologic and cardiac function.
Tests may include electrolyte testing, serum chemistry profile.
• Behavioral reaction to medication – Drug-related anxiety or agitation without systemic toxicity.
Tests may include CBC, serum chemistry profile to rule out medical causes.
• Underlying liver or kidney disease – Reduced ability to metabolize medications, increasing sensitivity.
Tests may include serum chemistry profile, urinalysis.
Safety, Psychology, & Peace of Mind
Waiting can feel reasonable when a pet seems only mildly affected, but drug effects can evolve unpredictably.
Assessment provides clarity when signs are ambiguous, especially with medications that act on the brain and heart.
Veterinary evaluation helps distinguish transient effects from escalating toxicity, reducing uncertainty and risk.
Same-day urgent care allows for monitoring during the period when complications are most likely to appear.
Many owners later report relief in knowing they didn’t wait when symptoms were unclear.
Frequently Asked Questions
Is antidepressant toxicity in dogs and cats an emergency?
Antidepressant toxicity in dogs and cats can range from mild to serious, depending on the specific medication, formulation, and the individual pet. Because outward appearance does not reliably indicate severity, this condition is treated as urgent. Same-day urgent care is recommended, especially if signs include agitation, tremors, weakness, vomiting, collapse, or seizures.
My pet seems normal now — can this still be serious?
Yes. Pets often hide illness, and antidepressant toxicity may temporarily improve even while the underlying effects continue internally. Apparent normal behavior does not reliably reflect internal stability, particularly with extended-release or combination medications. Veterinary assessment is appropriate even when symptoms appear mild or short-lived.
What if it only happened once or seems mild?
Even a single episode of antidepressant exposure can be clinically meaningful. Temporary improvement does not equal resolution, and waiting to see if signs return can delay recognition of more serious complications. Early assessment helps determine whether antidepressant toxicity is self-limiting or progressing.
Why are tests needed if we already know what was ingested?
Clinical signs alone cannot determine severity or internal impact in antidepressant toxicity. Diagnostic testing is how veterinarians assess organ function, heart rhythm, metabolic stability, and delayed effects that may not be visible externally. Testing replaces guesswork with clarity and helps guide safe monitoring decisions.
What should I do right now?
Do not rely on watchful waiting. Antidepressant toxicity in dogs and cats warrants veterinary assessment, particularly if signs are ongoing, worsening, or associated with neurologic, behavioral, or gastrointestinal changes. Same-day urgent care helps reduce risk and determine appropriate next steps.