NexGard Products for Fleas, Ticks, and Heartworms in Dogs and Cats

Written by Kathleen Claussen, DVM
Medically Reviewed by Joshua Conrad, PharmD on October 12, 2024
8 min read

The NexGard line of products for fleas, ticks, and heartworms in dogs and cats includes a topical product (applied to the skin) for cats and chewable tablets (given by mouth) for dogs.  NexGard products are approved by the FDA for various parasites in dogs and cats depending on which product is being used.  These include treatment and prevention of flea infestations, treatment and control of various ticks, prevention of heartworm disease, and treatment of intestinal roundworms, hookworms, and tapeworms.

All NexGard products for fleas and ticks contain the active ingredient afoxolaner (chewable tablets for dogs) or a form of it called esafoxolaner (topical liquid for cats).  Afoxolaner and esafoxolaner are classified as isoxazoline ectoparasiticides for treating and preventing fleas and ticks.  

For dogs, there are two NexGard chewable tablet options: NexGard Chews or NexGard Plus Chews.  NexGard Chews only contain afoxolaner and are only for fleas and ticks. In addition to afoxolaner, NexGard Plus Chews also contain moxidectin and pyrantel. Moxidectin is classified as a macrocyclic lactone antiparasitic that is used to prevent heartworm disease and to treat intestinal roundworms and hookworms. Pyrantel is a cholinergic agonist anthelmintic for the removal of roundworms and hookworms.  

NexGard Chews are approved for one month (every 30 days) of protection against fleas, and ticks.   NexGard Plus Chews are labeled for one month (every 30 days) of protection against fleas, ticks, heartworm disease, roundworms, and hookworms.  

There are also some other uses for NexGard products in dogs, including being effective against certain types of mange, bedbugs, ear mite infestations, sand flies, and some other infestations. These uses are “extra-label” or “off-label,” meaning that there is evidence of safe and effective use but the FDA has not approved that use.

For cats, NexGard Combo is a topical liquid given monthly (every 30 days) to treat fleas, ticks, heartworms, roundworms, hookworms, and tapeworms.  In addition to esafoxolaner, NexGard Combo contains eprinomectin and praziquantel.  Eprinomectin is an avermectin antiparasitic agent used to prevent heartworm disease and to treat intestinal roundworms and hookworms. Praziquantel is an anticestodal antiparasitic used to deworm for tapeworms. Extra-label use of NexGard Combo in cats includes ear mites, certain kinds of mange, vesical worms, cat lice, and treatment and prevention of feline lungworms.

NexGard products are usually well tolerated in animals. There is minimal risk for overdose, side effects, or drug interactions if used as labeled or as directed by your veterinarian.

NexGard products are available with a prescription from your veterinarian or from a veterinary pharmacy.

NexGard and NexGard Plus are chewable tablets that you give to your dog by mouth once a month (every 30 days). The chews can be given with or without food. If your dog throws up or acts sick after being given a chew on an empty stomach, give the next chew with food or a small treat. NexGard chews should be eaten completely to be fully effective. If your dog or puppy vomits some or all of a NexGard chewable within two hours of receiving the tablet, the event should be reported to your veterinarian and a new chewable should be given by mouth. Dogs and puppies should be at least 8 weeks old and weigh at least 4 pounds (1.8 kilograms) to use either NexGard or NexGard Plus.

NexGard Combo is a liquid that you apply to your cat’s skin between the shoulder blades once a month (every 30 days). NexGard Combo provides protection against treat fleas, ticks, heartworms, roundworms, hookworms, and tapeworms. Cats and kittens should be at least 8 weeks old and weigh at least 1.8 pounds (0.81 kilograms) to use NexGard Combo.

To apply NexGard Combo, make sure the skin at the back of the cat’s neck is dry and healthy. Using the appropriate tube of NexGard Combo, hold the applicator upright and remove the cap. Then part the hair and squeeze the entire contents of the tube directly onto the skin in one spot. Do not touch that area until it is completely dry. Avoid bathing your cat for two days after application. Do not allow your cat or other pets in the household to groom (rub or lick) the application site until it dries.

Always follow your veterinarian’s directions for giving medicines to animals. Remember to tell your veterinarian about any medicines, vitamins, supplements, or herbal therapies that you are giving your pet. Talk to your veterinarian before stopping any pet medicines.  

  • Afoxolaner and esafoxolaner are licensed by the FDA for treatment and control of fleas and various ticks in dogs and cats.
  • Eprinomectin, esafoxolaner, and praziquantel (NexGard Combo) is licensed by the FDA to protect against fleas, various ticks, heartworms, roundworms, hookworms, and tapeworms in cats and kittens.  
  • Afoxolaner in NexGard and NexGard Plus chews starts to kill fleas within 4 hours, with 99% effectiveness at 8 hours. Ticks are killed within 48 hours, with some ticks dying as fast as 8 to 12 hours with afoxolaner.
  • NexGard Combo (esafoxolaner/eprinomectin/praziquantel) starts to kill fleas on cats within 24 hours and ticks within 48 hours.

You and your veterinarian should monitor your pet for signs that the medicine is working (absence of live fleas or ticks), as well as for side effects of the medicine.  There is no routine lab monitoring needed with NexGard products.

If NexGard Plus or NexGard Combo is used for intestinal parasites, follow-up fecal (stool) tests may be done. If NexGard Plus or NexGard Combo is used for ear mites, follow-up ear tests may be done by your veterinarian.  

If NexGard chews are used for skin mite treatment in dogs, your veterinarian will monitor for improvement of symptoms (like hair loss and itching) as well as perform periodic skin tests.

Before giving NexGard Plus chews, dogs need to have a negative heartworm test.  The heartworm test should then be repeated yearly. If there are missed doses of NexGard Plus, a heartworm test should be repeated before restarting the medicine and then again in 6 months.  Before giving NexGard Combo for heartworms, your veterinarian may test the cat for the presence of existing heartworm disease if it is more than 6 months old.

Do not use a NexGard product in an animal that is allergic to its ingredients. Use with caution in dogs or cats that have a history of neurologic (nerve or brain) disease, including a history of seizures or epilepsy.  Do not use NexGard products in dogs or cats below the minimum age or weight on the product label.  Use them with caution in older or frail dogs and cats. Use NexGard Combo with caution in cats that already test positive for heartworms or have an unknown heartworm status. Do not allow your cat or their housemates to lick the application until dry (or for at least 30 minutes).  

Your pet should not be able to lick the site of application if using NexGard Combo. If it can, you may be applying it in the wrong spot. Other pets may try to groom or lick at the application site, especially cats that clean each other. Try to prevent this from happening, especially for 30 minutes after application or until the skin is dry. If your pet ingests the medicine, they will usually have excessive salivation (drooling) and may foam at the mouth. If your pet starts acting strangely, seek veterinary care.

Side effects are uncommon with NexGard products. Your cat may experience some irritation, redness, or hair changes at the application site of the topical product.  This should go away within a couple of days.  Seek veterinary care if it doesn’t go away, gets worse, or spreads. This could be an allergic reaction.

Other side effects with NexGard products include:

  • Vomiting
  • Diarrhea (loose stool)
  • Decreased appetite or hunger
  • Pruritus (Itching)
  • Lethargy (tiredness)

Afoxolaner and esafoxolaner are medicines in the isoxazoline drug class.  Isoxazoline drugs can cause neurologic (nerve and brain) side effects if given incorrectly or if an overdose occurs.  These issues include muscle tremors, difficulty walking, and seizures.  Other serious side effects may include nonstop vomiting or complete loss of appetite.

If you suspect that your pet is having a serious side effect or may have been overdosed, call your veterinary clinic immediately. If it is outside of regular office hours, you may contact a local emergency veterinary hospital or an animal poison control center. Note that fees may apply for emergency consultation.

You can reach the ASPCA Animal Poison Control Center at 888-426-4435 or the Pet Poison Helpline at 855-764-7661.

Using multiple medicines can sometimes change how your pet’s medicines work or increase your pet’s risk for serious side effects. Always tell your veterinarian about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements that your pet is using.

During clinical studies, NexGard products were used safely with vaccines, deworming products, antibiotics (including topicals), corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), anesthetics, sedatives, and antihistamines.

Some medicines that may interact with the ingredients in NexGard products are benzodiazepines such as alprazolam (Xanax) and diazepam (Valium), levamisole, and piperazine.  Other medicines to use cautiously with NexGard products are spironolactone, “azole” antifungals such as itraconazole or ketoconazole, cyclosporine, diltiazem, and erythromycin.  

This may not be a complete list of medicines that can interact with NexGard products. Always check with your veterinarian.

  • Keep NexGard products out of the reach of children. 
  • Wash your hands with soap after handling NexGard products. 
  • Do not handle NexGard products if you are allergic to any of the ingredients. 
  • Avoid getting NexGard Combo topical liquid in your eyes or on your skin and clothing. 
  • Avoid contact with the area of application of NexGard Combo on your cat until it is dry.

NexGard products are well tolerated by animals and the risk of an overdose is low. If you are concerned your pet is having an adverse reaction or if you think your pet has gotten more medicine than intended, call your veterinarian or veterinary emergency clinic immediately.

If your pet misses a dose, give the dose when you remember and then continue with the rest of the medicine at the correct time. Do not double the dose of the medicine.  

If more than 8 weeks have passed since the last dose of NexGard Plus, start the monthly chew again.  Your dog will need to have a heartworm test performed in 6 months to determine if there is heartworm disease. It takes 6 months from the bite of an infected mosquito till a dog may test positive for heartworm disease.

Store NexGard products in the original packaging at room temperature.  Protect them from light.