Nexgard for dogs refers to the use of an oral antiparasitic medication containing afoxolaner for certain flea and tick indications in dogs. In the United States, the medication is FDA-approved for dogs and puppies meeting specified age and weight requirements. It is used for the treatment and prevention of flea infestations and for the treatment and control of several tick species.

Understanding Nexgard for dogs involves considering its approved uses, administration, eligibility requirements, potential adverse reactions, and the circumstances in which veterinary guidance may be appropriate.

What Is Nexgard for Dogs?

Nexgard is an oral chewable medication containing afoxolaner. Afoxolaner belongs to the isoxazoline class of antiparasitic medications.

For its standard U.S. indications, Nexgard is approved for dogs and puppies at least eight weeks old and weighing at least four pounds. It is administered for a one-month period for the labeled flea and tick indications.

The medication is prescription-only in the United States. Its approved uses should be distinguished from other flea, tick, or parasite-control products that may have different active ingredients and indications.

Flea Control

One of the primary uses of Nexgard for dogs is the treatment and prevention of flea infestations. The FDA-approved labeling specifies activity against adult fleas and identifies Ctenocephalides felis as the flea species covered by the indication.

Fleas can cause itching and skin irritation. Some dogs may also develop flea allergy dermatitis, in which flea bites trigger an allergic skin response.

Flea control can involve more than treating the individual dog. Flea eggs and immature stages can remain in the surrounding environment, so veterinary advice may include environmental measures when an infestation is present.

Tick Control

Nexgard is also approved for the treatment and control of several tick species. The FDA's labeling includes black-legged ticks, American dog ticks, lone star ticks, brown dog ticks, and longhorned ticks. In March 2026, the FDA added an indication covering Gulf Coast tick infestations in eligible dogs and puppies.

The types of ticks encountered can vary by geographic area and season. Dogs that spend time outdoors may have different exposure risks from dogs that have limited outdoor activity.

The approved indication should therefore be considered alongside the dog's location and individual circumstances.

Administration and Weight

Nexgard for dogs is administered orally, with dosing determined according to body weight. The approved U.S. product is available in different strengths corresponding to weight ranges.

Dogs and puppies should meet the labeled minimum age and weight requirements before receiving the medication. The FDA specifies a minimum age of eight weeks and a minimum body weight of four pounds for the standard approved indications.

A veterinarian can determine whether the medication and the applicable dose are appropriate for an individual dog.

Potential Adverse Reactions

As with other medications, Nexgard can be associated with adverse reactions. FDA information has identified reactions including vomiting, diarrhea, decreased appetite, lethargy, and itching in dogs receiving the medication.

Because afoxolaner belongs to the isoxazoline class, neurologic adverse reactions are also an important safety consideration. The FDA states that products in this class have been associated with neurologic reactions such as muscle tremors, ataxia, and seizures. These reactions have been reported in animals both with and without a previous history of seizures.

A dog that develops unusual or serious symptoms after receiving the medication should be evaluated by a veterinarian.

Dogs With Neurologic Conditions

A dog's medical history can be relevant when considering an isoxazoline medication. Particular attention may be appropriate for dogs with a history of seizures or neurological disorders because of the potential for neurologic adverse reactions.

The FDA recommends discussing flea and tick treatment options with a veterinarian, particularly when an animal has individual health considerations.

Veterinary assessment can help determine whether the potential benefits and risks are appropriate for a particular dog.

New World Screwworm Emergency Authorization

In February 2026, the FDA issued an Emergency Use Authorization allowing Nexgard to be used for the treatment of New World screwworm infestations caused by larvae in dogs and puppies. This is an emergency authorization and is separate from Nexgard's established FDA-approved flea and tick indications.

The authorization applies under specific conditions established by the FDA. It should not be interpreted as a general change to all approved uses of the medication.

The FDA has noted that New World screwworm exposure risk is generally low for most dogs in the United States but can be higher for animals near the U.S.-Mexico border or those that have traveled to areas with active cases.

Veterinary Guidance

Nexgard for dogs is a prescription medication in the United States. Veterinary guidance can help determine whether its labeled uses correspond with an individual dog's age, weight, health history, parasite exposure, and other circumstances.

A veterinarian can also provide instructions regarding administration and what to do if an adverse reaction occurs.

Final Considerations

Nexgard for dogs is an oral afoxolaner medication used in the United States for specified flea and tick indications in eligible dogs and puppies. Its standard labeling includes dogs at least eight weeks old and weighing at least four pounds, with administration based on body weight.

Potential adverse reactions, including gastrointestinal and neurologic events, are important considerations. The 2026 FDA emergency authorization for New World screwworm represents a separate, specifically limited use.

Because parasite risks and individual health conditions differ among dogs, current FDA information and veterinary guidance remain important when considering Nexgard for dogs.