For most dogs, yes. The FDA says it "considers products in the isoxazoline class to be safe and effective for dogs and cats," and Bravecto (fluralaner) belongs to that class. The side effects on the US label are mostly mild: vomiting, decreased appetite, diarrhea and lethargy, each in fewer than 1 in 10 dogs in the field study.
The serious one is neurologic. The whole drug family carries a label warning for tremors, ataxia (wobbly, uncoordinated walking) and seizures, and seizures have been reported even in dogs with no seizure history. If your dog has ever had a seizure, tell your vet before the first dose.
Bravecto Side Effects in Dogs
Bravecto Chews were tested in a US field study: 224 dogs got Bravecto every 12 weeks and were followed for 182 days, while 70 dogs got another oral flea product every 4 weeks plus a tick collar. There were no serious adverse reactions. This is what was recorded, from the Bravecto Chews FDA label:
Side effect | Bravecto Chews (224 dogs, 182 days) | Comparison product (70 dogs, 84 days) |
|---|---|---|
Vomiting | 7.1% | 14.3% |
Decreased appetite | 6.7% | 0% |
Lethargy (tiredness) | 5.4% | 7.1% |
4.9% | 2.9% | |
Drinking more (polydipsia) | 1.8% | 4.3% |
Gas (flatulence) | 1.3% | 0% |
The comparison group was smaller, followed for less time and wore a tick collar, so this is not a ranking. Most dogs had none of these. In a separate lab study, one dog's upper lips swelled and reddened within an hour of its chew; it cleared up by the next morning without treatment.
Bravecto Topical, the spot-on for dogs, looked similar in its own field study of 221 dogs: vomiting 6.3%, hair loss 4.1%, diarrhea 2.7%, lethargy 2.7%, decreased appetite 1.4% and moist dermatitis or rash 0.9%, per the Bravecto Topical for Dogs label.
What the post-approval reports add
Once a drug is on the market, vets and owners report whatever happens after a dose. For the chews, the label lists, most reported first: vomiting, lethargy, diarrhea (with and without blood), anorexia, itching, drinking more, seizure, allergic reactions (hives, swelling, redness), skin reactions (crusts, pustules, rash), tremors and ataxia. The topical label adds application-site problems and behavior changes such as hyperactivity and vocalizing.
The label also says what these lists can't do: "It is not always possible to reliably estimate the adverse event frequency or establish a causal relationship to product exposure using these data." A report means something happened after a dose, not that Bravecto caused it or how often it happens. That is why scary stories circulate online, and why your vet still wants to hear about anything you notice.
The seizure warning: what the FDA actually says
In 2018 the FDA alerted pet owners and vets that some animals given isoxazoline flea and tick drugs, Bravecto among them, had muscle tremors, ataxia and seizures, and asked the makers to add a warning. Every Bravecto label for dogs now carries it:
"Fluralaner is a member of the isoxazoline class. This class has been associated with neurologic adverse reactions including tremors, ataxia, and seizures. Seizures have been reported in dogs receiving isoxazoline class drugs, even in dogs without a history of seizures. Use with caution in dogs with a history of seizures or neurologic disorders."
The FDA's fact sheet for pet owners keeps both halves together: isoxazolines "have been associated with neurologic adverse reactions, including muscle tremors, ataxia, and seizures in some dogs and cats," and "although most dogs and cats haven't had neurologic adverse reactions, seizures may occur in animals without a prior history." Credelio, Nexgard and Simparica are in the same class, so switching between those brands does not leave the warning behind.
In the topical field study, two of 221 Bravecto dogs with no seizure history had a seizure, one about 18 days and one 76 days after the first dose (the second dog had just started fluoxetine). If your dog has a seizure, your vet will also look at other things that can cause seizures in dogs.
When to call your vet
Call your vet today if your dog:
- vomits more than once, or has diarrhea that keeps going
- won't eat, or seems unusually tired for more than a day
- has redness, hair loss, crusts or itching where the topical went on
Call now (or go to an emergency vet) if your dog:
- has a seizure, trembles, or walks wobbly or drunk
- has a swollen face or lips, hives, or trouble breathing
- ate extra chews or got more than one dose: call your vet or a poison line, the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661
The FDA's advice comes first: "If your dog or cat experiences any adverse event while using an isoxazoline product, first consult your veterinarian." You can also report a suspected side effect to Merck Animal Health at 1-800-224-5318 or to the FDA at 1-888-FDA-VETS.
Which Dogs Need Extra Care?
The Chews, Topical and 1-Month labels list "no known contraindications," so no group of dogs is ruled out. Some dogs still need a conversation first. Tell your vet about these:
- A seizure history or another neurologic disorder. The label says "use with caution." That is not a ban. Talk to your vet about options; they weigh your dog's history against the flea and tick risk where you live.
- Pregnant, nursing or breeding dogs. Tell your vet if your dog is pregnant, nursing or used for breeding. The Chews label reports a study in which Beagles got up to three times the top label dose, three or four times, 8 weeks apart: 7 pups from 2 of the 10 treated mothers had limb deformities, enlarged hearts or spleens, or cleft palate at necropsy, and none in the untreated group did. Post-approval reports include birth defects, stillbirth and abortion after treatment of breeding females. The label asks vets to review these findings before using Bravecto in a breeding female. The topical's breeding safety was evaluated with the oral form, and the 1-Month chew and Bravecto Quantum have not been evaluated in breeding, pregnant or nursing dogs.
- Young or tiny dogs. Bravecto Chews and Topical are labeled for dogs at least 6 months old and 4.4 pounds. Bravecto 1-Month chews can start at 8 weeks and 4.4 pounds.
- Older or frail dogs. WebMD's vet-written guide advises caution.
- Dogs on other medicines. WebMD's guide names maropitant (Cerenia), NSAID pain relievers and warfarin as possible interactions, usually not a major concern. In the field study, Bravecto was used with vaccines, dewormers, antibiotics and steroids without reactions. Tell your vet about everything your dog takes, supplements included.
What Bravecto Does (and Doesn't) Cover
Bravecto's active ingredient, fluralaner, blocks chloride channels in the nervous system of fleas and ticks, which kills them once they feed on a treated dog. It is a prescription drug: federal law limits it to use by or on the order of a licensed veterinarian.
One dose of the chew or topical covers, per the US labels:
- Fleas for 12 weeks. It treats and prevents infestations, which also helps dogs with flea allergy dermatitis.
- Black-legged ticks, American dog ticks and brown dog ticks for 12 weeks. The chew also covers the Asian longhorned tick; the topical label does not list it.
- Lone star ticks for only 8 weeks. That is why the label allows a dose every 8 weeks for dogs likely to meet them.
It does not cover heartworm or intestinal worms, so your dog still needs a separate heartworm preventive if your vet recommends one. It also kills rather than repels: fleas and ticks have to bite to get a dose, so you may still see the odd one. The chew began killing fleas within two hours in a lab study.
Vets also use Bravecto for a type of mange called generalized demodicosis. In the US that is extra-label use (not on the label), so it is your vet's call.
The Bravecto family for dogs now has four members:
- Bravecto Chews, by mouth every 12 weeks.
- Bravecto Topical Solution, on the skin every 12 weeks.
- Bravecto 1-Month Chews, monthly from 8 weeks of age. They cover fleas and the same four ticks as the chews for a month, and lone star ticks from 6 months of age.
- Bravecto Quantum, an injection your vet gives every 12 months (every 8 months where lone star ticks are a risk), from 6 months of age. Its label also lists the Gulf Coast tick. The FDA approved it in July 2025. Its label adds that allergic reactions, including anaphylaxis, have been reported, and a dermatologist interviewed by AAHA named the trade-off: a long-lasting side effect can't be removed faster than the drug wears off.
Bravecto Dosage Chart for Dogs
Bravecto is dosed by weight band: your dog gets the one chew or tube made for its weight. The labels use pounds; kilograms are converted.
For information only. These are typical published dose ranges, not a prescription and not medically verified for your pet. Your veterinarian sets the dose after examining your pet. Never start, stop or change a medicine without their OK.
Product | Dog's weight | Amount | How often | How given | Source |
|---|---|---|---|---|---|
Bravecto Chews (dogs 6 months and older, 4.4 lb and up) | 4.4 to 9.9 lb (2.0 to 4.5 kg) | One 112.5 mg chew | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | By mouth, with food | |
Bravecto Chews | Over 9.9 to 22 lb (4.5 to 10 kg) | One 250 mg chew | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | By mouth, with food | |
Bravecto Chews | Over 22 to 44 lb (10 to 20 kg) | One 500 mg chew | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | By mouth, with food | |
Bravecto Chews | Over 44 to 88 lb (20 to 39.9 kg) | One 1000 mg chew | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | By mouth, with food | |
Bravecto Chews | Over 88 to 123 lb (39.9 to 55.8 kg) | One 1400 mg chew | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | By mouth, with food | |
Bravecto Chews | Over 123 lb (55.8 kg) | The label uses a combination of chews; your vet will tell you which | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | By mouth, with food | |
Bravecto Topical Solution (dogs 6 months and older, 4.4 lb and up) | 4.4 to 9.9 lb (2.0 to 4.5 kg) | One 112.5 mg tube | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | On the skin, starting between the shoulder blades | |
Bravecto Topical Solution | Over 9.9 to 22 lb (4.5 to 10 kg) | One 250 mg tube | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | On the skin, starting between the shoulder blades | |
Bravecto Topical Solution | Over 22 to 44 lb (10 to 20 kg) | One 500 mg tube | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | On the skin, starting between the shoulder blades | |
Bravecto Topical Solution | Over 44 to 88 lb (20 to 39.9 kg) | One 1000 mg tube | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | On the skin, starting between the shoulder blades | |
Bravecto Topical Solution | Over 88 to 123 lb (39.9 to 55.8 kg) | One 1400 mg tube | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | On the skin, starting between the shoulder blades | |
Bravecto Topical Solution | Over 123 lb (55.8 kg) | The label uses a combination of tubes; your vet will tell you which | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | On the skin, starting between the shoulder blades | |
Bravecto 1-Month Chews (dogs 8 weeks and older, 4.4 lb and up; lone star ticks from 6 months) | 4.4 to 9.9 lb (2.0 to 4.5 kg) | One 45 mg chew | Once a month | By mouth, with food | |
Bravecto 1-Month Chews | Over 9.9 to 22 lb (4.5 to 10 kg) | One 100 mg chew | Once a month | By mouth, with food | |
Bravecto 1-Month Chews | Over 22 to 44 lb (10 to 20 kg) | One 200 mg chew | Once a month | By mouth, with food | |
Bravecto 1-Month Chews | Over 44 to 88 lb (20 to 39.9 kg) | One 400 mg chew | Once a month | By mouth, with food | |
Bravecto 1-Month Chews | Over 88 to 123 lb (39.9 to 55.8 kg) | One 560 mg chew | Once a month | By mouth, with food | |
Bravecto 1-Month Chews | Over 123 lb (55.8 kg) | The label uses a combination of chews; your vet will tell you which | Once a month | By mouth, with food | |
Bravecto Quantum (dogs 6 months and older) | Weighed at the visit | Given by your vet | Every 12 months; every 8 months if your dog may meet lone star ticks | Injection by your vet |
Dose calculator · Bravecto (fluralaner)
Bravecto size calculator for dogs
Not a prescription. For information only. These are typical published dose ranges, not a prescription and not medically verified for your pet. Your veterinarian sets the dose after examining your pet. Never start, stop or change a medicine without their OK.
Only give what your vet prescribed.
All doses in this calculator
| Pet | Use | Typical dose | How often | Route | Source |
|---|---|---|---|---|---|
| Dog | Fleas and ticks, Bravecto Chews (12-week chew) | 2 to 4.49 kg (4.4 to 9.9 lb): One 112.5 mg chew (4.4 to 9.9 lb); 4.49 to 9.98 kg (9.9 to 22 lb): One 250 mg chew (over 9.9 to 22 lb); 9.98 to 20 kg (22 to 44 lb): One 500 mg chew (over 22 to 44 lb); 20 to 39.9 kg (44 to 88 lb): One 1000 mg chew (over 44 to 88 lb); 39.9 to 55.8 kg (88 to 123 lb): One 1400 mg chew (over 88 to 123 lb)FDA label weight bands, for dogs 6 months and older, 4.4 lb and up. Over 123 lb the label uses a combination of chews; your vet will tell you which. Use with caution in dogs with a history of seizures or neurologic disorders; talk to your vet about options. Tell your vet if your dog is pregnant, nursing or used for breeding. | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | By mouth, with food | Bravecto Chews FDA label (Merck Animal Health, DailyMed) |
| Dog | Fleas and ticks, Bravecto Topical Solution (12-week spot-on) | 2 to 4.49 kg (4.4 to 9.9 lb): One 112.5 mg tube (4.4 to 9.9 lb); 4.49 to 9.98 kg (9.9 to 22 lb): One 250 mg tube (over 9.9 to 22 lb); 9.98 to 20 kg (22 to 44 lb): One 500 mg tube (over 22 to 44 lb); 20 to 39.9 kg (44 to 88 lb): One 1000 mg tube (over 44 to 88 lb); 39.9 to 55.8 kg (88 to 123 lb): One 1400 mg tube (over 88 to 123 lb)FDA label weight bands, for dogs 6 months and older, 4.4 lb and up. Over 123 lb the label uses a combination of tubes; your vet will tell you which. Ask your vet or vet tech to show you how to apply it the first time. Use with caution in dogs with a history of seizures or neurologic disorders; talk to your vet about options. Tell your vet if your dog is pregnant, nursing or used for breeding. | Every 12 weeks; every 8 weeks if your dog may meet lone star ticks | On the skin, starting between the shoulder blades | Bravecto Topical for Dogs FDA label (Merck Animal Health, DailyMed) |
| Dog | Fleas and ticks, Bravecto 1-Month Chews | 2 to 4.49 kg (4.4 to 9.9 lb): One 45 mg chew (4.4 to 9.9 lb); 4.49 to 9.98 kg (9.9 to 22 lb): One 100 mg chew (over 9.9 to 22 lb); 9.98 to 20 kg (22 to 44 lb): One 200 mg chew (over 22 to 44 lb); 20 to 39.9 kg (44 to 88 lb): One 400 mg chew (over 44 to 88 lb); 39.9 to 55.8 kg (88 to 123 lb): One 560 mg chew (over 88 to 123 lb)FDA label weight bands, for dogs 8 weeks and older, 4.4 lb and up (lone star ticks from 6 months). Over 123 lb the label uses a combination of chews; your vet will tell you which. Use with caution in dogs with a history of seizures or neurologic disorders; talk to your vet about options. Tell your vet if your dog is pregnant, nursing or used for breeding. | Once a month | By mouth, with food | Bravecto 1-Month Chews FDA label (Merck Animal Health, DailyMed) |
Only give what your vet prescribed, at the dose they set.
- One chew or tube per dose, sized to the weight band. Over 123 pounds, the label uses a combination of chews or tubes; your vet will tell you which.
- Give the chews with food: fluralaner is absorbed less on an empty stomach.
- If your dog's weight has changed, ask your vet whether the size you have still fits before the next dose.
- Bravecto Quantum is not in the calculator: your vet weighs your dog and gives the injection at the visit.
Seizure history, a planned litter, or a pregnant or nursing dog: ask your vet first.
Too much Bravecto?
In the label's safety study, puppies got up to 5 times the top label dose, three times, with no clinically relevant drug effects. Reassuring, but not a reason to wait. If your dog ate extra chews, got a dose meant for a bigger dog or got two doses close together, call your vet or a poison line now: ASPCA Animal Poison Control (888) 426-4435 or Pet Poison Helpline (855) 764-7661. Have the box handy, and don't try to treat it at home.
How to Give Bravecto
Chews. Most dogs take them like a treat: in the field study, 80.7% of doses were eaten voluntarily within 5 minutes and another 12.5% when offered with food. Give the chew with a meal, then wash your hands with soap and water. Store chews where dogs, cats and kids can't reach them: the label warns about accidental ingestion and overdose.
Topical. Ask your vet or vet tech to show you the first time; the label says they should. Then:
- Put on gloves and twist the cap one full turn until the seal breaks (the cap stays on).
- With your dog standing or lying with its back level, part the fur between the shoulder blades and place the tip on the skin.
- Squeeze gently in one or more spots, starting between the shoulder blades and moving along the back, so the liquid doesn't run off.
Keep children from touching the spot for 2 hours. Don't let other pets lick it: WebMD notes that pets who swallow the liquid usually drool and may foam at the mouth. The liquid is highly flammable, so apply it away from heat and flames. Bathing or swimming from 3 days after application did not reduce how well it worked, so wait those 3 days.
Missed a dose? Give it when you remember, then count the next due date from that day. Don't double up.
Bravecto FAQ
Do I need a prescription for Bravecto?
Yes. Federal law limits Bravecto to use by or on the order of a licensed veterinarian. According to Merck Animal Health, your vet can give it at the clinic or write a prescription you can fill at an authorized online pet retailer.
Can I use Bravecto all year?
Yes. The label says treatment can start at any time of year and continue year round without a break. If you spot flea dirt between doses, tell your vet.
Can I give my dog's Bravecto to my cat?
No. The dog products are labeled for dogs only. Cats have their own products (Bravecto Topical for Cats and Bravecto Plus for Cats), for cats at least 6 months old and 2.6 pounds. Ask your vet which one fits your cat.
I found a dead tick on my dog. Is Bravecto working?
Probably, yes. Bravecto kills ticks after they attach and feed, so a dead tick still stuck to the skin is expected. Remove it and keep checking after walks.
How long does Bravecto stay in a dog's body?
After a chew, fluralaner's half-life is 9.3 to 16.2 days, and small amounts (too low to protect) can be measured up to 112 days later. That long tail is why one dose lasts 12 weeks, and why a side effect can't be washed out quickly.
Originally written by Dr. Catharina Hjorth. Updated by the I Love Veterinary editorial team.
Sources
- Merck Animal Health: BRAVECTO (fluralaner) Chews, FDA label, DailyMed
- Merck Animal Health: BRAVECTO (fluralaner topical solution) for Dogs, FDA label, DailyMed
- Merck Animal Health: BRAVECTO 1-MONTH (fluralaner) Chews for Dogs, FDA label, DailyMed
- Merck Animal Health: BRAVECTO QUANTUM, FDA label, DailyMed
- FDA: Fact Sheet for Pet Owners and Veterinarians about Potential Adverse Events Associated with Isoxazoline Flea and Tick Products
- FDA: Animal Drug Safety Communication on potential neurologic adverse events with certain flea and tick products
- FDA: FDA approves first long-acting flea and tick treatment for dogs
- WebMD: Bravecto for Fleas, Ticks, and Heartworms in Dogs and Cats
- AAHA Trends: Bravecto Quantum, insight from a dermatologist
- Merck Animal Health: Get Bravecto
- ASPCA: Animal Poison Control Center
- Pet Poison Helpline
This article is for general information and is not a substitute for advice from your veterinarian.
