Brand: NEXGARD ®


FORMULATION: «tablets» for oral administration; may be chewable, flavored, coated, etc., depending on the country


CHEMICAL CLASS of the active ingredient(s): ISOXAZOLINE


PARASITES CONTROLLED* (spectrum of activity): Fleas, Ticks (in the USA: Dermacentor variabilisIxodes scapularis, Amblyomma americanum); in the EU: Dermacentor reticulatus, Ixodes ricinus, Rhipicephalus sanguineus)


USA and other countries

  • Dogs, 4.0 to 10.0 lbs. 1.8 to 4.5 kg bw: 1 tablet with 11.3 mg afoxolaner (equivalent to 6.3 to 2.5 mg/kg afoxolaner)
  • Dogs, 10.1 to 24 lbs. 4.6 to 10.9 kg bw: 1 tablet with 28.3 mg afoxolaner (equivalent to 6.2 to 2.6 mg/kg afoxolaner)
  • Dogs, 24.1 to 60 lbs. 11 to 27.2 kg bw: 1 tablet with 68 mg afoxolaner (equivalent to 6.2 to 2.5 mg/kg afoxolaner)
  • Dogs, 60.1 to 121 lbs. 27.3 to 54.9 kg bw: 1 tablet with 136 mg afoxolaner (equivalent to 5.0 to 2.3 mg/kg afoxolaner)
  • Dogs, >121 lbs. ≈ >54.9 kg bw: administer the appropriate combination of tablets

EU and other countries

  • Dogs, 2.0 to 4.0 kg 4.4 to 8.8 lbs. bw: 1 tablet with 11.3 mg afoxolaner (equivalent to 5.7 to 2.8 mg/kg afoxolaner)
  • Dogs, 4.0 to 10 kg ≈ >8.8 to 22.0 lbs. bw: 1 tablet with 28.3 mg afoxolaner (equivalent to 7.1 to 2.8 mg/kg afoxolaner)
  • Dogs, 10 to 25 kg ≈ >22.0 to 55.1 lbs. bw: 1 tablet with 68 mg afoxolaner (equivalent to 6.8 to 2.7 mg/kg afoxolaner)
  • Dogs, >25 to 50 kg≈ >55.1 to 110.2 lbs. bw: 1 tablet with 136 mg afoxolaner (equivalent to 5.4 to 2.7 mg/kg afoxolaner)
  • Dogs, >50 kg ≈ >110.2 lbs. bw: administer the appropriate combination of tablets

* Can be slightly different in some countries: read the product label!


  • LD50 (acute oral) in rats: n.a. for the tablets. >1000 mg/kg for the a.i. afoxolaner (source: EMEA)
  • Estimated Hazard Class according to the WHO: not applicable for veterinary medicines

In September 2018 the FDA of the USA has alerted pet owners and veterinarians about potential neurological adverse events following the use of products containing isoxazolines. Some treated animals have experienced adverse events such as muscle tremors, ataxia (lack of voluntary coordination of muscle movements), and seizures. This regards all products containing isoxazolines. Most treated animals will not show such adverse drug reactions, but some may be affected.

Suspected poisoning? Read the article on afoxolaner safety in this site.

WARNING !!!: Never use on cats tablets approved only for use on dogs, and vice-versa. Never use on cats or small dogs tablets approved for large dogs. Learn more about tablets and their safety.

You may be interested in the following articles in this site dealing with the general safety of veterinary products:


Risk of resistance development? YES, very low in fleas, mainly the cat flea, Ctenocephalides felis

Afoxolaner has been introduced in 2014. It belongs to the isoxazolines (together with fluralaner, the active ingredient of BRAVECTO), a new chemical class of insecticides introduced in 2010s, from which afoxolaner and fluralaner are the first commercial products at all. Isoxazolines have a mode of action that is different from all other insecticides currently used against fleas or ticks, and shows no cross-resistance with them. Consequently there are no reports on resistance to isoxazolines. However, fleas have developed resistance to several other insecticides (e.g. carbamates, organophosphates and pyrethroids) and are certainly capable of becoming resistant to isoxazolines as well. Experience shows that prolonged and uninterrupted use of any insecticide on fleas bears the risk of resistance development. 

Alternatives to prevent resistance through product rotation:

*F = effective against fleas; T = effective against ticks.

These alternative products may not be available in all countries, or may not be available as tablets.

Resistance of fleas to carbamates, organophosphates and pyrethroids is not uncommon in several countries, including the USA.

Learn more about resistance and how it develops.


Are the active ingredients of this product ORIGINAL* or GENERICS**?

  • Afoxolaner: ORIGINAL (introduced in 2013, first described by DU PONT DE NEMOURS)

*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.

COUNTRIES where this product is marketed: USA, the EU, Canada, Australia, New Zealand, etc.

Click here to learn more about GENERIC vs. ORIGINAL drugs.


NEXGARD is a once-a-month flea+tick tablet with afoxolaner for dogs from MERIAL (now BOEHRINGER INGELHEIM). Whereas in the past there were numberless once-a-month spot-ons against fleas + ticks, until the launch of NEXGARD no once-a-month tablet against fleas + ticks was available, only against fleas (e.g. COMFORTIS, PROGRAM), or against fleas + roundworms, including heartworms (e.g. TRIFEXIS, SENTINEL = PROGRAM PLUS).

NEXGARD was approved in the EU against Dermacentor reticulatus, Ixodes ricinus and Rhipicephalus sanguineus, the most important tick species affecting dogs in Europe. In the USA it is approved against Dermacentor variabilis, Ixodes scapularis and Amblyomma americanum, important in the USA in dogs. In the USA it is also approved for the prevention of Borrelia burgdorferi infections as a direct result of killing Ixodes scapularis vector ticks.

It must be considered that there are other tick species in Europe (e.g. Dermacentor marginatus, Dermacentor pictusHaemaphysalis spp, Hyalomma spp, Rhipicephalus bursa, etc.) and also in the USA that can infect dogs in addition to the ones controlled by this product. It is not known whether NEXGARD controls such tick species as well. 

Afoxolaner is is a broad-spectrum isoxazoline insecticide and acaricide introduced in the 2010s (by MERIAL, licensed from DU PONT). It has a systemic mode of action, i.e. after oral administration it gets into the blood of the pet and reaches the fleas and ticks during their blood meal. It starts to kill fleas about 8 hours and ticks about 48 hours after administration. Administered about every 4 weeks it controls established flea infestations and prevents flea population development in the pets environment, but only if all the dogs and cats in the same household are treated against fleas. Ticks are killed during about 4 weeks after treatment.

Systemic products (tablets for oral administration, injectables) have several general advantages over topical products (spot-on, insecticide-impregnated collars, shampoos, soaps, sprays, powders, etc):

  • They do not contaminate the pet's hair coat: avoiding contact with the pets after administration is not necessary for children or adults.
  • The active ingredient reaches the parasites through the blood, everywhere in the pet's body, whereas topical products may leave some body parts (e.g. the ears, between the legs, etc.) insufficiently protected.
  • Efficacy is independent from exposure to dirt, sun, shampooing, washings, rain, baths, dirt, etc., whereas topical products can be washed away, or broken down by sunlight, etc.

But they have also a few disadvantages:

  • The parasite has to bite and suck blood first before it is killed or sterilized, i.e. they may transmit several diseases before they are killed.
  • Orally administered products (tablets, suspensions, pastes, etc.) may be vomited and treatment needs to be repeated.
  • Administration of tablets may be less convenient than administration of spot-ons.
  • The choice of products for oral or injectable administration is smaller than for topical administration.

For an overview and a list of the most popular pet antiparasitics for flea, tick, lice and/or mite control click here.


This article IS NOT A PRODUCT LABEL. It offers complementary information that may be useful to veterinary professionals and users that are not familiar with veterinary antiparasitics. 

Information offered in this article has been extracted from publications issued by manufacturers, government agencies (e.g. EMEA, FDA, USDA, etc.) or in the scientific literature. No guarantee is given on its accuracy, integrity, sufficiency, actuality and opportunity, and any liability is denied. Read the site's DISCLAIMER.

In case of doubt contact the manufacturer or a veterinary professional.