NexGard(®) is a relatively new medicine which can be given to dogs to kill ticks and fleas. It contains the active ingredient afoxolaner which spreads through the dog’s bloodstream after being ingested. When parasites feed on the blood of the dog the drug enters their bodies and causes death by overloading the nervous system.

The medicine kills the following ticks:

  • American Dog tick
  • Black-legged tick
  • Brown Dog tick
  • Lone star tick

How long does it take to kill fleas?

Nexgard kills all adult fleas within 24 hours before they can lay eggs.

Recommended Dosage

Note: It’s important to speak to the vet before giving NexGard to your dog.

The minimum target dosage is 1.14 mg/lb of active ingredient (afoxolaner) per month. NexGard products are color-coded for use in different sized dogs.

Weight of dog

Colored box to use

4 – 10 lbsOrange box (11.3 mg afoxolaner per tablet)
10.1 – 24 lbsBlue box (28.3 mg afoxolaner per tablet)
24.1 – 60 lbsPurple box (68 mg afoxolaner per tablet)
60.1 – 121 lbsRed box (136 mg afoxolaner per tablet)
Over 121 lbsUse an appropriate combination.

You only need to give one tablet each month for protection. You should not give the medicine to any dog under 4 lbs or less than 8 weeks of age.

Note: For dogs over 121 lbs an appropriate combination should be used. For example a 140 lb dog requires a minimum dosage of 159.6 mg afoxolaner, so you could give one tablet from the red box with one tablet from the blue box each month.

Safety Information

The medicine is very safe for most dogs. Side effects are rare and in high amounts up to five times the recommended dose only vomiting is expected. However, dogs with seizure disorders are at a higher risk of a bad reaction and could experience seizures after being given NexGard.

Pregnancy & Nursing Notice: Safety has not yet been established under these circumstances, so we recommend avoiding use in pregnant or lactating animals.

Safety Guidelines

Though it is a safe medication, it could be dangerous if used incorrectly. When giving NexGard to your pet you should follow these guidelines:

  • Do not give to dogs who weigh less than 4 lbs
  • Do not give to dogs who are less than 8 weeks old
  • Practice caution or avoid use entirely in seizure-prone pets
  • Store well out of reach of children and pets

Warning: This medicine should never be taken by a human or any animal other than a dog.

What Is It Used For?

NexGard is given to dogs to kill adult fleas and to prevent flea infestations. It is also used to kill ticks and control existing tick infestations. It does not act as a repellant, parasites must bite and feed on your pet’s blood before the medicine takes effect.

Side Effects

Though uncommon, the following adverse effects are possible:

  • Vomiting
  • Diarrhea
  • Lethargy
  • Loss of appetite
  • Dry or flaky skin
  • Seizures *

* This reaction is only expected in those with a history of seizures.


NexGard website
Dr. D. Primovic