CBD for Dog Seizures in Canada: What 3 Vet Trials Actually Found

Straight answer: CBD is not a replacement for seizure medication, but it has been tested as an add-on in three controlled trials in dogs with drug-resistant epilepsy, and if your veterinarian agrees to try it alongside your dog's prescribed treatment, the oil we recommend is Pure Majesty Pets Vet-Strength CBD Oil for Dogs — 30 mg CBD + 25 mg CBDA + 5 mg CBG in every mL, no intentionally added THC and a certificate of analysis on every batch. In those trials, dogs given CBD on top of their usual drugs had fewer seizure days or fewer seizures than on placebo, yet the share of dogs whose seizures fell by half or more was only clearly higher in one small study. Liver enzymes rose in all three. Below: what each trial found, the numbers people misquote, how CBD fits with phenobarbital, the emergency signs and a 12-week log to share with your vet.

If you are still choosing a product, our guide to the best CBD for dogs compares six oils sold in Canada on mg per mL, THC and cost per mg in C$. This guide answers a narrower question that owners of epileptic dogs ask every day: is there real evidence behind CBD for dog seizures, and how do you try it without putting your dog at risk? The short version is that the research is promising but small, and every study gave CBD in addition to antiseizure drugs, never instead of them.

First: When a Seizure Is an Emergency

No supplement belongs in an emergency. The International Veterinary Epilepsy Task Force defines the two situations that need a veterinarian immediately:

• Status epilepticus: a seizure lasting more than 5 minutes, or two or more seizures without your dog fully recovering consciousness in between.
• Cluster seizures: two or more seizures within 24 hours.

A first-ever seizure also needs a vet exam, because seizures can come from causes other than idiopathic epilepsy, and those causes need their own diagnosis. Everything below is about dogs that already have a diagnosis and a treatment plan.

What the Three Dog Trials Found

All three studies enrolled dogs with idiopathic epilepsy whose seizures continued despite standard medication, and all three added CBD or a CBD-rich oil to that medication.

Honest note: none of these studies used Pure Majesty Pets CBD Oil. The McGrath trial was funded by the company that made its oil, and the Garcia trial's product contained THC. The results describe those products in those dogs — not a promised result for any oil, including ours.

The Numbers That Get Misquoted

Three figures travel around the internet without their context:

• "89% of dogs had fewer seizures." This came from the 2019 university press release: 8 of the 9 dogs that finished on CBD had at least some reduction. But the trial's own measure of real response — a drop of 50% or more — was similar in the CBD and placebo groups.
• "CBD cut seizures by a third." The 33% is a median across a small group. Some dogs improved a lot, others very little, and two dogs on CBD were withdrawn because they became wobbly.
• "CBD reduced seizures by 24%." In the 2023 trial, the 24% figure is seizure days. Total seizures actually went up in both phases — just far less with CBD than with placebo.

Read together, the trials suggest CBD may help some dogs with hard-to-control epilepsy as an add-on, and that blood levels and dose seem to matter. A 2022 review co-written by veterinary neurologists concluded that it is not yet possible to give clear-cut recommendations for CBD in canine epilepsy (Potschka et al., 2022). The AKC Canine Health Foundation is funding follow-up work on dosing, formulations and long-term safety.

CBD Is an Add-On, Never a Swap

Every dog in these trials stayed on its prescribed antiseizure drugs. Stopping or lowering phenobarbital, potassium bromide, levetiracetam or zonisamide without your veterinarian can trigger withdrawal seizures and cluster seizures. If you want to try CBD, the order is simple:

1. Talk to the vet who manages the epilepsy — ideally with baseline bloodwork and a few months of seizure records in hand.
2. Keep every prescribed dose exactly as it is.
3. Add one product at a time, so any change can be traced.
4. Log seizures for at least 12 weeks, the length of each trial phase, before judging.

In Canada, cannabis products — including CBD for animals — fall under Health Canada and the Cannabis Act; talk to your veterinarian before starting.

For a broader look at side effects, liver enzymes and overdose, read our guide to whether CBD is safe for dogs.

CBD and Phenobarbital: What Is Known About Interactions

CBD is processed by liver enzymes that also handle many drugs, so an interaction is a reasonable worry. Here is what the dog data show so far:

• Garcia 2022: no differences in blood levels of zonisamide, phenobarbital or bromide between the CBD + CBDA and placebo phases.
• Rozental 2023: phenobarbital levels rose 11% during the CBD phase vs −1% on placebo. Not statistically significant, but the authors said it may point to an interaction the study was too small to confirm.
• Doran et al., 2022: in nine healthy beagles given CBD with phenobarbital, no significant interaction was found in how either was absorbed or cleared.

The practical takeaway: your vet may want to recheck phenobarbital levels and liver values after CBD is added. That is not a reason to skip CBD — it is the reason to involve your vet.

Liver Checks: The Side Effect That Showed Up Every Time

The most consistent finding across all three seizure trials was a rise in liver enzymes:

• ALP (alkaline phosphatase) rose with CBD in McGrath 2019 and mildly in Garcia 2022.
• ALT rose significantly in Rozental 2023, and two dogs also had raised bile acids at the end, a sign of reduced liver function. The authors advise monitoring liver enzymes.
• Other effects: decreased appetite and vomiting were more common on CBD in the 2023 trial; somnolence and short-lived wobbliness appeared in the 2022 trial at similar rates to placebo.

Phenobarbital itself can raise liver enzymes, which makes a baseline blood panel before adding CBD — and a recheck a few weeks later — especially useful.

Why THC Content Matters for a Dog on Daily Medication

Two of the three seizure trials used full-spectrum oils. The Garcia product listed 1.2 mg of THC and 1.3 mg of THCA per mL; for a 25 kg (55 lb) dog at 2 mg/kg of CBD + CBDA, that works out to roughly 1 mg of THC per dose, twice a day. The Merck Veterinary Manual lists lethargy, wobbliness, vomiting and dribbling urine among the signs of THC toxicity in dogs — signs that are hard to tell apart from medication side effects or a post-seizure phase. For a dog already on sedating antiseizure drugs, an oil with no intentionally added THC removes one variable. Our guide to full spectrum vs isolate CBD for dogs explains the difference in detail.

Study Doses in mL (For the Conversation With Your Vet)

The Garcia trial's oil is the closest published match to our formula: roughly equal CBD and CBDA (about 30 + 31 mg/mL) dosed at 2 mg/kg twice daily. Here is that study-level amount with Pure Majesty Pets CBD Oil at 60 mg of total cannabinoids per mL. Your veterinarian sets the actual amount and may start lower.

The 2023 trial used a higher CBD-only amount (4.5 mg/kg twice daily) after a lower dose showed no effect, so any increase is a decision for your vet, with liver checks. Give each dose with food at the same times every day — CBD is absorbed better with a meal, and consistent timing makes your log easier to read. Every weight is in our CBD dosage chart for dogs.

The 12-Week Seizure Log to Bring to Your Vet

Seizure frequency swings naturally from month to month, which is why every trial used months-long phases and a placebo comparison. At home, your log is the closest thing to that. Record:

Keep at least two to three months of records before starting CBD if you can, so there is a baseline to compare against. If stress around visitors or travel is part of the picture, our guide to CBD for dog anxiety covers what the calm studies used.

What It Costs With Our Oil

At C$46.00 for 60 mL, a study-level routine of 2 mg/kg twice daily costs about C$0.51 a day for a 10 kg (22 lb) dog and C$1.28 a day for a 25 kg (55 lb) dog — about C$38.33 for 30 days for the larger dog. To see how other oils sold in Canada compare on price and mg per mL, see our best CBD oil for dogs comparison.

Why Pure Majesty Pets CBD Oil Fits an Add-On Plan for Dogs With Seizures

• CBD + CBDA in a ratio close to the Garcia trial oil — 30 mg CBD and 25 mg CBDA per mL, plus 5 mg CBG. That trial tested another company's product; our formula has not been studied in epileptic dogs.
• No intentionally added THC — one less variable for a dog already on sedating medication.
• Every cannabinoid quantified, so your vet knows exactly what is being added and in what amount.
• A certificate of analysis on every batch — cannabinoids, THC and contaminants.
• 60 mg/mL — small, measurable volumes with a 1 mL oral syringe, from 0.15 mL for a 4.5 kg (10 lb) dog.
• MCT oil with sunflower lecithin and natural bacon flavour, given with food; no added water, glycerin or xylitol.
• About C$1.28 a day for a 25 kg (55 lb) dog at study-level dosing, made in North America under GMP standards, with free shipping.

Pure Majesty Pets also makes liquid collagen for dogs (462 mg Type I & III collagen + 48 mg UC-II per serving) for joint, skin and coat support; with an epileptic dog, ask your vet before adding any supplement. Ready to discuss it with your vet? See Pure Majesty Pets CBD Oil for Dogs →

Red Flags With CBD for Dogs With Seizures

• Any product or person suggesting you stop or cut antiseizure medication — never do this without your vet.
• Cure or "seizure-free" promises — no CBD product is FDA-approved for any use in animals.
• No mg per mL on the label — you cannot match a study dose or report it to your vet.
• No batch COA, or a COA with THC but no THCA result.
• Human CBD products or the human prescription drug without veterinary direction — different strengths, and some human products contain xylitol.
• Changing CBD brand or dose mid-trial — it makes your log impossible to interpret.
• Poor appetite, vomiting, yellowing gums or eyes, or new wobbliness after starting — call your vet.

The Bottom Line

CBD for dog seizures is an add-on with early, mixed but genuine evidence: in three controlled trials, dogs on CBD plus their usual drugs had fewer seizure days or fewer seizures than on placebo, while clear 50% responses were uncommon and liver enzymes rose. It is never a replacement for antiseizure medication, and it should start with your vet, a baseline blood panel and a seizure log.

If your vet agrees to a trial, Pure Majesty Pets Vet-Strength CBD Oil for Dogs gives you CBD and CBDA in measured amounts, no intentionally added THC and a COA on every batch — the details your vet needs to supervise it properly.