Watching your dog have a seizure is one of the most frightening experiences a pet owner can have. The sudden loss of control, the paddling limbs, the vocalizing, the disorientation afterward — it looks worse than it usually is, but it always warrants veterinary attention. And when seizures happen more than once, or when they happen in clusters, the question shifts from "what just happened" to "what is causing this and how do we control it."

This article covers the three broad categories of seizure causes in dogs, how the diagnostic workup distinguishes between them, what treatment options exist, and what long-term medication monitoring requires. It draws on the 2026 ACVIM consensus landscape, a large 2026 retrospective study of seizure treatment in U.S. primary-care practices, and the January 2026 FDA full approval of KBroVet (potassium bromide chewable tablets) for canine idiopathic epilepsy.

Quick answer

Seizures in dogs have three main categories of cause: extracranial (metabolic, toxic, or systemic problems outside the brain), structural intracranial (brain tumors, encephalitis, trauma, vascular events), and idiopathic epilepsy (recurrent seizures with no identifiable cause, typically beginning between one and five years of age).

The diagnostic workup starts with a thorough history, physical exam, and neurological exam, followed by screening bloodwork (CBC, chemistry, resting cortisol, pre- and post-prandial bile acids) and urinalysis to rule out metabolic causes. If metabolic causes are excluded and the clinical picture fits idiopathic epilepsy, many primary-care veterinarians will start anti-seizure medication without advanced imaging (MRI) — though MRI and CSF analysis are needed to definitively exclude structural brain disease.

First-line anti-seizure medications include phenobarbital, potassium bromide (KBroVet, which received FDA full approval in January 2026), imepitoin, and increasingly, levetiracetam and zonisamide. Long-term monitoring requires periodic bloodwork (CBC, chemistry, serum drug levels) to assess efficacy, safety, and organ function — because several of these medications carry risks of hepatotoxicity, pancreatitis, and bone-marrow suppression that are manageable when caught early but dangerous when ignored.

What a seizure looks like in a dog

A seizure is a sudden, uncontrolled burst of electrical activity in the brain. In dogs, seizures typically fall into these categories:

• Generalized (grand mal): loss of consciousness, collapse, stiffening followed by paddling or jerking of all four limbs, jaw champing, salivation, possible urination or defecation. This is the type most owners recognize.
• Focal (partial): affects one part of the body — twitching of one limb, the face, or one side. The dog may remain conscious and aware. Focal seizures can sometimes generalize (spread to involve the whole body).
• Cluster seizures: two or more seizures within a 24-hour period. Cluster seizures are a medical concern because they can progress to status epilepticus.
• Status epilepticus: a single seizure lasting longer than 5 minutes, or multiple seizures without recovery of consciousness between them. This is a life-threatening emergency requiring immediate veterinary care.

After a seizure, most dogs enter a post-ictal phase lasting minutes to hours: disorientation, pacing, blindness, hunger, restlessness, or lethargy. This phase is normal but can be distressing to watch.

The three categories of seizure causes

Extracranial causes (outside the brain)

These are problems originating elsewhere in the body that secondarily affect brain function:

Extracranial causes are often identifiable with basic bloodwork and history, and the seizures resolve when the underlying problem is treated.

Structural intracranial causes (brain disease)

These are diseases within the brain itself:

Structural causes are identified by advanced imaging (MRI) and sometimes CSF analysis. They are more common in dogs younger than 6 months or older than 5–6 years at first seizure onset, and in dogs with abnormal interictal (between-seizure) neurological exams.

Idiopathic epilepsy

Idiopathic epilepsy (also called primary epilepsy) is the most common cause of recurrent seizures in dogs. It is defined by:

• First seizure between 6 months and 6 years of age (most commonly 1–4 years).
• Normal interictal neurological examination.
• No identifiable metabolic or structural cause on diagnostic workup.

Idiopathic epilepsy is believed to have a genetic component in many breeds, including Labrador Retrievers, Golden Retrievers, German Shepherd Dogs, Beagles, Belgian Tervurens, and others. It affects an estimated 0.5–0.82% of dogs in primary-care populations, based on large epidemiological studies in multiple countries.

A definitive diagnosis of idiopathic epilepsy requires MRI and CSF analysis to be normal. In practice, many primary-care veterinarians diagnose idiopathic epilepsy based on the clinical picture (age, normal exam, normal bloodwork, characteristic seizure pattern) and start treatment without advanced imaging. This is a reasonable approach in classic cases, but owners should understand that MRI is needed to truly exclude structural disease.

The diagnostic workup

Step 1: History and physical and neurological examination

The most important part of the workup is often the history. Key questions include:

• What did the seizure look like? (Generalized, focal, duration, number of episodes)
• When did it happen? (Time of day, relationship to meals, sleep, or activity)
• How has the dog been between seizures? (Normal, or showing neurological abnormalities)
• Has there been any exposure to toxins, medications, or recent illness?
• Is there a family history of seizures?

The neurological examination checks mental status, posture, gait, cranial nerves, spinal reflexes, and pain perception. A normal interictal neurological exam supports (but does not prove) idiopathic epilepsy. An abnormal exam — persistent deficits between seizures — suggests structural brain disease.

Step 2: Screening bloodwork

Minimum database to rule out extracranial causes:

• CBC: anemia, infection, inflammation.
• Serum chemistry: kidney function (BUN, creatinine, SDMA), liver enzymes (ALT, ALP), glucose, electrolytes (sodium, potassium, calcium, phosphorus), total protein, albumin.
• Pre- and post-prandial bile acids: screens for hepatic encephalopathy and portosystemic shunts. A fasting and 2-hour post-meal sample is standard.
• Resting cortisol: if below 2 µg/dL, perform ACTH stimulation test to rule out hypoadrenocorticism (Addison's disease), which can cause seizures.
• Urinalysis: complements kidney-function assessment.
• Blood pressure: severe hypertension can contribute to neurological signs.

Step 3: Advanced diagnostics (when indicated)

If screening bloodwork is normal and the clinical picture does not clearly fit idiopathic epilepsy, or if the dog has an abnormal neurological exam, the next step is referral for advanced diagnostics:

• MRI (magnetic resonance imaging): the gold standard for imaging the brain. Identifies tumors, inflammation, strokes, malformations, and other structural lesions. Requires general anesthesia.
• CSF (cerebrospinal fluid) analysis: collected during the same anesthetic episode as MRI. Evaluates for inflammation, infection, and neoplastic cells. CSF analysis is contraindicated if MRI reveals significantly elevated intracranial pressure.
• Infectious-disease titers: for Toxoplasma, Neospora, Bartonella, and other regional infectious causes of encephalitis, depending on geographic risk and clinical suspicion.

When primary-care veterinarians start treatment without MRI

It is common and generally accepted practice to start anti-seizure medication in dogs with classic idiopathic epilepsy presentations (age 1–5, normal interictal exam, normal bloodwork, no suggestive history of toxin exposure or trauma) without performing MRI. However, the following features should prompt consideration of advanced imaging or referral:

• First seizure before 6 months or after 6 years of age.
• Abnormal interictal neurological exam.
• Focal seizures that suggest a structural lesion.
• Seizures that are difficult to control despite appropriate medication.
• Cluster seizures or status epilepticus at initial presentation.
• Rapid progression in seizure frequency or severity.

Anti-seizure medications

The choice of anti-seizure medication depends on the dog's age, seizure type and frequency, comorbidities, owner compliance (ability to administer twice-daily medication), cost, and the veterinarian's comfort level with each drug.

Phenobarbital

Phenobarbital has been the most widely prescribed anti-seizure medication in veterinary medicine for decades. A 2026 retrospective study of 752 dogs treated for idiopathic epilepsy in U.S. primary-care practices (Pompermaier, Morrison, Stabile, and De Risio, published in Frontiers in Veterinary Science) found phenobarbital to be the most commonly used first-line therapy.

• Mechanism: enhances GABA-mediated inhibition in the brain.
• Dosing: typically started at 2–3 mg/kg orally every 12 hours, then adjusted based on serum drug levels and seizure control.
• Monitoring: serum phenobarbital trough levels (drawn just before a dose) should be checked 2–3 weeks after starting or changing the dose, targeting 15–35 µg/mL. CBC and chemistry (especially ALT, ALP, and liver function) should be monitored every 6–12 months.
• Adverse effects: sedation and ataxia (especially early, usually transient), polyuria/polydipsia, polyphagia, weight gain. Rare but serious: hepatotoxicity (more likely at higher serum levels and with long-term use), neutropenia, anemia.
• Key consideration: phenobarbital induces hepatic enzymes, which can accelerate the metabolism of other drugs — including levetiracetam, which may require higher or more frequent dosing when used concurrently.

Potassium bromide (KBroVet)

In January 2026, the FDA granted full approval to KBroVet (potassium bromide chewable tablets, Pegasus Laboratories) for control of seizures in dogs with idiopathic epilepsy — making it the first drug to receive full FDA approval specifically for this indication. It had previously held conditional approval since 2021.

• Mechanism: enhances neuronal hyperpolarization by replacing chloride ions, raising the seizure threshold.
• Dosing: maintenance dose typically 20–30 mg/kg/day orally, divided once or twice daily. Loading doses (400–600 mg/kg divided over several days) can achieve therapeutic levels faster but cause sedation.
• Monitoring: serum bromide levels, targeting approximately 1–3 mg/mL. Steady state takes 2–4 months with maintenance dosing (faster with loading). Levels should be checked 2–3 months after starting and then every 6–12 months.
• Adverse effects: sedation, ataxia, polyuria/polydipsia, polyphagia. Rare: pancreatitis (a known association — avoid in dogs with a history of pancreatitis). Severe bromide intoxication (bromism) causes depression, ataxia, weakness, and in extreme cases stupor or coma.
• Key consideration: bromide levels are affected by dietary chloride intake. Abrupt diet changes (especially to higher-salt foods) can lower bromide levels and trigger seizures. Dogs on potassium bromide should have a stable, consistent diet.

Levetiracetam (Keppra)

Levetiracetam is increasingly used in veterinary medicine as both a primary and adjunctive anti-seizure medication. The 2026 Frontiers study found it commonly used as add-on therapy in primary-care practices.

• Mechanism: modulates synaptic vesicle protein SV2A, though the exact anticonvulsant mechanism is not fully understood.
• Dosing: immediate-release 20–60 mg/kg orally every 8 hours; extended-release 30 mg/kg orally every 12 hours. Extended-release tablets must not be crushed, broken, or chewed.
• Monitoring: routine therapeutic drug monitoring is not typically required, which is a practical advantage. Serum levels can be measured if non-compliance or drug interaction is suspected.
• Adverse effects: generally well tolerated. Sedation and ataxia occur at higher doses but are less frequent and less severe than with phenobarbital or bromide. Minimal hepatic metabolism — safe for dogs with liver disease.
• Key consideration: the short half-life (~3 hours for immediate-release) means doses must be given on a strict schedule. Missed doses can trigger breakthrough seizures. Phenobarbital may accelerate levetiracetam clearance, requiring dose adjustment.

Zonisamide

Zonisamide is another newer-generation anti-seizure medication used as adjunctive therapy:

• Dosing: 5–10 mg/kg orally every 12 hours.
• Monitoring: serum levels can be measured but are not routinely required. Periodic CBC and chemistry are recommended.
• Adverse effects: sedation, ataxia, GI upset. Rare: blood dyscrasias.
• Key consideration: sulfonamide derivative — avoid in dogs with known sulfonamide hypersensitivity.

Imepitoin (Pexion)

Imepitoin is FDA-approved for noise aversion in dogs and is used as an anti-seizure medication in some countries. Its role in long-term seizure management is more established in Europe than in the United States.

• Dosing: 10–30 mg/kg orally every 12 hours.
• Monitoring: no routine therapeutic drug monitoring assays are commercially available.
• Adverse effects: sedation, ataxia, polydipsia, polyphagia. Some studies report higher rates of cluster seizures with imepitoin monotherapy compared to phenobarbital, and behavioral changes (aggression) have been noted.
• Key consideration: less established than phenobarbital or potassium bromide for idiopathic epilepsy in the U.S. market, where KBroVet's recent full approval has strengthened the bromide option.

A note on not stopping medication suddenly

This is important enough to state clearly: anti-seizure medication should never be stopped abruptly. Sudden discontinuation — especially of phenobarbital or bromide — can trigger rebound seizures, including cluster seizures and status epilepticus, that are worse than the dog's baseline. If a medication change is needed, it should be done as a gradual taper under veterinary supervision.

At-home rescue medications

For dogs with known epilepsy, veterinarians may prescribe emergency medications that owners can administer at home during a prolonged seizure or cluster event:

• Rectal diazepam (Valium): a benzodiazepine administered via a syringe and soft tube into the rectum. Can shorten seizure duration and reduce severity. Owners are trained by their veterinarian on proper technique and dosing.
• Intranasal midazolam: another benzodiazepine applied inside the nostril. Some veterinary neurologists prefer intranasal midazolam over rectal diazepam because absorption may be more reliable.
• Pulse-dose levetiracetam: some veterinarians prescribe a higher dose of levetiracetam to be given at the start of a cluster event, in addition to the dog's regular maintenance medication.

These rescue medications are not a replacement for maintenance anti-seizure therapy. They are a safety net for breakthrough events. Ask your veterinarian whether a rescue plan is appropriate for your dog.

What monitoring actually requires

Long-term seizure management is not "prescribe and forget." The monitoring schedule varies by drug but generally includes:

The seizure diary is the single most useful monitoring tool. Owners should record: date, time, duration, description (generalized vs. focal, severity), recovery time, and any potential triggers. This diary allows the veterinarian to assess whether the current treatment is working, whether a dose adjustment is needed, and whether the seizure pattern is changing (which may indicate disease progression or the need for additional diagnostics).

When seizures are not controlled

Approximately 20–30% of dogs with idiopathic epilepsy are not adequately controlled on a single medication. These dogs may benefit from:

• Combination therapy: adding a second anti-seizure drug (most commonly levetiracetam or zonisamide as an add-on to phenobarbital or bromide).
• Dose adjustment: optimizing serum levels within the therapeutic range before adding a second drug.
• Referral to a veterinary neurologist: for advanced imaging, CSF analysis, EEG, and specialized treatment protocols including potentially ketogenic diet trials and emerging neuromodulation approaches.

What owners should ask their veterinarian

• "What type of seizure does my dog appear to be having, and what are the most likely causes at this age?"
• "What bloodwork do we need to rule out metabolic causes?"
• "Does my dog need an MRI, or is it reasonable to start with medication based on the current clinical picture?"
• "What medication do you recommend first, and what are the most important side effects to watch for?"
• "How often should we check blood levels and organ function?"
• "Should I keep a seizure diary, and what should I record?"
• "At what point should we consider referral to a neurologist?"

Sources

• Pompermaier E, Morrison JA, Stabile F, De Risio L. Retrospective study on canine idiopathic epilepsy treatment in primary care practices in the United States. Front Vet Sci. 2026;13:1723038. https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2026.1723038/full
• U.S. Food and Drug Administration. FDA grants full approval of a drug to control seizures in dogs with idiopathic epilepsy (KBroVet). January 21, 2026. https://www.fda.gov/animal-veterinary/cvm-updates/fda-grants-full-approval-drug-control-seizures-dogs-idiopathic-epilepsy
• dvm360. FDA grants full approval for canine idiopathic epilepsy medication. https://www.dvm360.com/view/fda-grants-full-approval-for-canine-idiopathic-epilepsy-medication
• Merck Veterinary Manual. Epilepsy in small animals. https://www.merckvetmanual.com/nervous-system/epilepsy-in-small-animals/epilepsy-in-small-animals
• Veterinary Information Network (VIN). Veterinary Partner — Seizure disorders in dogs. https://veterinarypartner.vin.com/doc?id=4951440&pid=19239
• VCA Animal Hospitals. Testing for seizures. https://vcahospitals.com/know-your-pet/testing-for-seizures
• De Risio L, Bhatti S, Muñana K, et al. International veterinary epilepsy task force consensus proposals. BMC Vet Res. 2015;11:176.
• Nature Index. Canine epilepsy: diagnosis and management strategies. https://www.nature.com/nature-index/topics/l4/canine-epilepsy-diagnosis-and-management-strategies
• AKC Canine Health Foundation. New discoveries are changing the future for dogs with seizures. https://www.akcchf.org/educational-resources/library/articles/new-discoveries-are-changing-the-future-for-dogs-with-seizures