Bravecto starts killing fleas within 2 hours of giving it to your dog, reaching 88% flea kill within 4 hours and 100% within 12 hours. Ticks take a bit longer, with kill activity beginning within 8 hours. That speed makes it one of the faster-acting flea and tick preventives available.
Flea Kill Timeline
The active ingredient in Bravecto, fluralaner, absorbs into your dog’s bloodstream quickly after the chew is swallowed. Fleas that bite your dog pick up the compound and begin dying within 2 hours. By the 4-hour mark, nearly 9 out of 10 fleas on your dog are dead. Full flea kill, meaning every flea on your dog, happens within 12 hours of that first dose.
This speed matters if your dog already has a flea problem when you give the first dose. You should see a dramatic drop in scratching and visible fleas within the same day. New fleas that jump onto your dog in the following weeks are killed at the same pace, which breaks the flea life cycle and prevents reinfestation over time.
Tick Kill Timeline by Species
Ticks generally need more time than fleas to absorb a lethal dose because they feed more slowly. Bravecto begins killing ticks within 8 hours. But the exact window depends on which tick species is involved.
- Black-legged ticks, American dog ticks, and brown dog ticks are covered for the full 12-week protection period. Black-legged ticks and similar species see greater than 98% kill within 12 hours after treatment or new infestation.
- Brown dog ticks can take up to 48 hours for full efficacy after treatment or new attachment.
- Lone star ticks are covered for only 8 weeks rather than 12, so if you live in an area where lone star ticks are common, you may need to redose sooner.
- Asian longhorned ticks are also covered for the full 12-week window.
Keep in mind that ticks still need to attach and begin feeding before they’re exposed to fluralaner in your dog’s blood. Bravecto doesn’t repel ticks. It kills them after they bite. This means you may still see a tick on your dog, but it will die before it can transmit most tick-borne diseases, which typically require 24 to 48 hours of attachment.
How Bravecto Kills Parasites
Fluralaner targets a specific part of the insect nervous system. Fleas and ticks rely on chemical signals called GABA to regulate nerve activity. Fluralaner blocks the receptors for these signals, which throws the parasite’s nervous system into overdrive. Within minutes of exposure at the cellular level, nerve firing becomes rapid and chaotic, followed by total nerve shutdown. The result is paralysis and death.
This mechanism is highly selective to invertebrates. The receptors fluralaner targets in fleas and ticks are structurally different from those in mammals, which is why the compound is toxic to parasites but not to your dog. Fluralaner also doesn’t share resistance patterns with older flea and tick treatments, so it remains effective against parasites that have developed tolerance to other products.
Why Giving It With Food Matters
Feeding your dog before or during the dose makes a significant difference in how well Bravecto is absorbed. In a pharmacokinetic study, dogs that ate food with their Bravecto chew absorbed 2.5 times more of the drug overall compared to dogs that took it on an empty stomach. Peak blood levels were 2.1 times higher in fed dogs.
The good news is that food doesn’t slow the onset. Dogs reached peak blood concentrations at roughly the same time whether they’d eaten or not, so feeding doesn’t delay how fast fleas start dying. What it does is raise the overall amount of fluralaner circulating in the bloodstream, which strengthens protection throughout the full 12-week period. If your dog takes the chew without eating, the drug still works, but you’re leaving a lot of its potential on the table. Give it with a meal or a generous treat.
How Long Protection Lasts
A single Bravecto chew protects against fleas and most tick species for 12 weeks (about 3 months). The lone star tick is the exception, with coverage lasting 8 weeks. This extended duration comes from fluralaner’s unusually long half-life in dogs. It stays in the bloodstream at effective levels far longer than most monthly preventives.
Throughout those 12 weeks, any new fleas that jump on your dog are killed within hours, maintaining continuous protection without a gap. Some pet owners worry that efficacy fades toward the end of the dosing period, but studies show greater than 98% flea and tick kill lasting the full 12 weeks when the chew is given with food as directed.
Age and Weight Requirements
Bravecto chews are approved for dogs and puppies 6 months of age and older, weighing at least 4.4 pounds. Puppies younger than 6 months haven’t been shown to maintain 12 weeks of protection, likely because their faster metabolism clears the drug sooner. If your puppy is under 6 months, your vet can recommend an alternative until they’re old enough for Bravecto.
The chews come in weight-based dosing tiers, so your dog gets the right amount of fluralaner for their size. Using the correct weight range is important both for safety and for ensuring the drug reaches effective blood levels that last the full dosing period.