NexGard is a popular monthly chewable flea and tick preventative for dogs manufactured by Boehringer Ingelheim. Its active ingredient, afoxolaner, belongs to the isoxazoline class of parasiticides, which has become the dominant approach to flea and tick prevention in modern veterinary medicine. NexGard is FDA-approved for dogs and puppies 8 weeks of age or older weighing 4 pounds or more. It requires a veterinary prescription and is one of the most frequently prescribed flea and tick products in the United States.
What Is NexGard Used For?
NexGard is prescribed for the prevention and treatment of flea and tick infestations in dogs:
- Flea treatment and prevention — kills adult fleas (Ctenocephalides felis) before they can lay eggs
- Tick prevention and treatment — kills multiple tick species including:
- Black-legged tick (deer tick, Ixodes scapularis)
- American dog tick (Dermacentor variabilis)
- Lone Star tick (Amblyomma americanum)
- Brown dog tick (Rhipicephalus sanguineus)
NexGard begins killing fleas within four hours and achieves full flea kill within eight hours of administration. For ticks, NexGard kills attached ticks within 48 hours.
Note: NexGard alone does not prevent heartworm disease or treat intestinal parasites. For broader protection, your veterinarian may recommend NexGard Plus (afoxolaner + moxidectin + pyrantel), which adds heartworm, roundworm, and hookworm prevention, or may pair NexGard with a separate heartworm preventative.
How Does NexGard Work?
Afoxolaner is an isoxazoline that works by disrupting the nervous system of fleas and ticks. Specifically, it inhibits ligand-gated chloride channels (GABA receptors and glutamate-gated chloride channels) in insect and arachnid nerve cells. This causes uncontrolled nerve activity, paralysis, and death of the parasites.
After your dog chews and swallows the NexGard tablet, afoxolaner is absorbed into the bloodstream and distributed throughout the body. When fleas or ticks bite your dog and begin feeding on blood, they ingest the afoxolaner and are killed. The drug maintains effective concentrations for a full month, providing continuous protection between doses.
Because isoxazolines target invertebrate-specific chloride channels, they have a wide margin of safety in mammals. However, all isoxazoline products carry an FDA class-wide label warning about the potential for neurologic adverse events in some dogs (see Side Effects section).
Dosage
NexGard is dosed by weight and given once monthly. Your veterinarian will prescribe the correct size for your dog. Each package contains tablets formulated for specific weight ranges:
| Dog’s Weight | NexGard Tablet Size | Afoxolaner per Tablet |
|---|---|---|
| 4.0 - 10.0 lbs (1.8 - 4.5 kg) | Small | 11.3 mg |
| 10.1 - 24.0 lbs (4.6 - 10.9 kg) | Medium | 28.3 mg |
| 24.1 - 60.0 lbs (11.0 - 27.2 kg) | Large | 68 mg |
| 60.1 - 121.0 lbs (27.3 - 54.9 kg) | Extra Large | 136 mg |
| Over 121 lbs (55+ kg) | Combination of tablets as directed by your vet | Varies |
The minimum effective dose is 1.14 mg/lb (2.5 mg/kg). NexGard should be given every 30 days, year-round in most regions, or as recommended by your veterinarian based on local parasite risk.
How to Give NexGard to Your Dog
- NexGard is a soft, beef-flavored chewable that most dogs accept readily as a treat.
- Give the chewable with or without food. Some dogs may accept it more easily with a meal.
- Ensure your dog chews and swallows the entire tablet rather than swallowing it whole, as this ensures proper absorption.
- If your dog vomits within two hours of dosing, consider re-dosing and consult your veterinarian.
- Set a monthly reminder to maintain consistent protection. Gaps in dosing leave your dog vulnerable to flea and tick infestations.
- Store unused tablets in the original packaging until ready to use.
Side Effects
NexGard is generally well tolerated. The most commonly reported side effects in clinical trials were mild and transient.
| Common Side Effects | Serious Side Effects (Contact Your Vet) |
|---|---|
| Vomiting | Seizures |
| Diarrhea or soft stools | Tremors or muscle twitching |
| Lethargy | Ataxia (uncoordinated movement, stumbling) |
| Decreased appetite | Severe or prolonged vomiting or diarrhea |
| Dry or flaky skin | Signs of allergic reaction |
FDA Isoxazoline Class Warning: The FDA has issued a class-wide alert for all isoxazoline flea and tick products (including NexGard, Simparica, Bravecto, and Credelio) regarding potential neurologic adverse events. These events, including seizures, tremors, and ataxia, have been reported in some animals, including those with no prior history of neurologic conditions. While these events are considered uncommon, dogs with a history of seizures may be at increased risk. Discuss your dog’s health history with your veterinarian before starting any isoxazoline product.
Drug Interactions
NexGard has not been evaluated in combination with all other medications. Inform your veterinarian about all drugs and supplements your dog receives. There are no widely reported major drug interactions with NexGard, but general precautions include:
- Other isoxazolines: Do not use multiple isoxazoline products simultaneously.
- Seizure medications: Dogs on anticonvulsant therapy should be carefully monitored. Consult your vet about the risk-benefit assessment.
- Other flea/tick products: Generally unnecessary and not recommended to use topical flea/tick products concurrently with NexGard unless specifically directed by your vet.
Contraindications
- Dogs under 8 weeks of age or weighing less than 4 pounds
- Dogs with a known hypersensitivity to afoxolaner
- Dogs with a history of seizures should be evaluated carefully by a veterinarian before starting NexGard (risk-benefit discussion recommended)
- Safety in breeding, pregnant, or lactating dogs has not been evaluated
Storage
- Store at 68-77degF (20-25degC).
- Keep in original packaging until use.
- Excursions to 59-86degF (15-30degC) are permitted.
- Keep out of reach of children and other animals.
Cost & Availability
NexGard is a prescription-only product with no generic version available.
- Approximate cost (6-month supply, medium dog): $90-$120
- Per-month cost: $15-$25 per dose depending on dog size and retailer
- Available through veterinary clinics, online pet pharmacies (with prescription), and some retail pharmacies
- NexGard Plus (with heartworm and intestinal worm protection) costs approximately $110-$150 for a 6-month supply
Year-round flea and tick prevention is recommended in most regions of the United States, so budget for 12 months of coverage.
Frequently Asked Questions
What is the difference between NexGard and NexGard Plus? NexGard contains only afoxolaner and protects against fleas and ticks. NexGard Plus contains afoxolaner plus moxidectin and pyrantel, adding protection against heartworm disease, roundworms, and hookworms. NexGard Plus provides broader all-in-one parasite protection in a single monthly chewable.
How does NexGard compare to Simparica Trio? Both are monthly chewable isoxazoline products. NexGard (standalone) covers fleas and ticks only, while Simparica Trio covers fleas, ticks, heartworm, roundworms, and hookworms. NexGard Plus is the more direct comparison to Simparica Trio, as both are all-in-one products. The choice between them depends on factors including your dog’s health profile, local parasite risks, and your veterinarian’s recommendation. Both carry the same FDA isoxazoline class warning.
Is NexGard safe for puppies? NexGard is FDA-approved for puppies 8 weeks of age and older weighing at least 4 pounds. This is one of the youngest minimum ages among flea and tick chewables. Always consult your veterinarian before starting any flea and tick prevention in puppies.
Does NexGard protect against heartworm? No. NexGard alone does not prevent heartworm disease. You will need a separate heartworm preventative (such as Heartgard Plus) or can ask your veterinarian about NexGard Plus, which includes heartworm prevention.
Can I use NexGard for my cat? No. NexGard is approved for dogs only. Cats require species-appropriate flea and tick prevention. Consult your veterinarian about suitable options for cats.
Sources & References
- FDA - NexGard Product Information and Label
- FDA - Fact Sheet for Pet Owners: Isoxazoline Flea and Tick Products
- Merck Veterinary Manual - Ectoparasiticides
- VCA Hospitals - NexGard (Afoxolaner)
- PetMD - NexGard for Dogs
- Boehringer Ingelheim - NexGard Product Page
Verification Notes
NexGard dosing, weight ranges, and minimum age (8 weeks, 4 lbs) are consistent with the FDA-approved label. The isoxazoline class-wide neurologic adverse event warning is accurately reflected as an FDA communication applying to all products in this class. Cost estimates ($90-120 for 6-month supply, medium dog) are consistent with current US retail pricing data from the research compiled for this site. The distinction between NexGard and NexGard Plus is based on FDA-approved label indications. Parasite coverage details (flea and tick species) align with the product label.