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Afoxolaner (Nexgard)
Revised: August 24, 2023
Published: January 01, 2000

(For veterinary information only)

The size of the tablet/medication is NOT an indication of a proper dose. Never administer any drug without your veterinarian's input. Serious side effects or death can occur if you use drugs on your pet without your veterinarian's advice. 

It is our policy not to give dosing information over the internet.

Brand Name: Nexgard

Available in 11.3 mg, 28.3 mg, 68 mg, 136 mg chewable tablets


Historically, flea control was a labor-intensive process involving sprays, dips, foggers, yard treatments, powders, and more. As technology progressed, products became safer and more convenient, culminating in a whole “next generation” of products, starting with Program® in 1995 and Advantage® and Frontline® not long after. For the first time, flea control could be performed once a month in the simple form of a chewable tablet or smear of topical oil. These products represented a revolution in flea control, but the revolution did not stop there. Today, parasite control has proliferated into dozens of products controlling different combinations of organisms and with many administration options.

Afloxolaner was released by Merial Animal Health (now Boehringer Ingelheim) in 2014 as a beef-flavored chewable prescription medication called "Nexgard®."  In 2023, Nexgard plus® (containing afoxolaner, moxidectin, and pyrantel pamoate) was released for broader canine parasite protection. Other related products include an oral product for dogs called Nexgard Spectra® (in Europe) where afoxolaner is combined with milbemycin and a topical feline product called Nexgard Combo® using the derivative afoxolaner combined with eprinomectin and praziquantel for deworming.

A valid patient-doctor relationship is required to obtain a prescription for afoxolaner. Afoxolaner kills fleas and ticks only and has no inherent activity against intestinal worms or heartworm. There are four ticks of concern in the U.S. (see our tick product comparison chart for more details), and afoxolaner will kill all of them, plus several additional tick species not on the official approval label.

As for fleas, afoxolaner kills them before they are able to lay eggs, so a flea sterilizer is not necessary in the tablet.

How This Medication Is Used

Afoxolaner lasts one month and can be used in puppies and dogs eight weeks of age and older, weighing at least 4 lbs. It should not be used in cats. (As mentioned, cats have a topical product in the Nexgard family based on esafoxalaner, which is slightly different.)

Afoxolaner can be given either with or without food.

Side Effects

The possible side effects reported include nausea/vomiting (4% of dogs), diarrhea (3% of dogs), dandruffy coat (3% of dogs), lethargy (less than 2% of dogs) and appetite loss (less than 2% of dogs). Most dogs that exhibited one of these side effects only exhibited them after the first dose and not with subsequent doses.

If a dog vomits within two hours of administration of an afoxolaner tablet, a new tablet should be given. If vomiting occurs after two hours, re-dosing is not necessary.

Interactions With Other Drugs

There are no known drug interactions with afoxolaner.

Concerns and Cautions

Afoxolaner has not been evaluated in pregnant or nursing animals, so it is recommended not to use in this situation.

Afoxolaner kills fleas by causing an over-stimulation of the insect nervous system. This leads fleas to be extra active just before they die; this increase in activity can lead the fleas to be more visible. Your pet may also be temporarily extra itchy by the extra flea activity when the dose is first given.

The manufacturer recommends caution in pets with known seizure disorders. Muscle tremors and seizures can occur in animals with no prior history of such as well.

If a monthly dose is skipped, fleas and ticks will be able to complete their life cycle freely. Do not double up on the next dose, though; simply give the afoxalaner when you remember to do so.

Store at room temperature in the sealed container provided by the manufacturer.

See more information on afoxolaner.

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