Section: Clinical Methods & Interventions

Nexgard For Dogs

NexGard (afoxolaner) is a popular oral chewable that provides monthly protection against fleas and ticks for dogs. As a prescription medication, it offers convenience for pet owners who prefer an oral alternative to topical treatments. Understanding how NexGard works, its proper use, and what to expect can help you make informed decisions for your dog's parasite control.

Quick Q&A: Common Questions

Question: How quickly does NexGard start killing fleas?
Answer: NexGard begins killing fleas within 30 minutes of administration and reaches peak effectiveness within 4 hours. It continues to kill fleas and ticks for a full 30 days, providing reliable monthly protection.

How NexGard Works

NexGard contains the active ingredient afoxolaner, which belongs to the isoxazoline class of parasiticides. Afoxolaner targets the nervous system of fleas and ticks by blocking GABA and glutamate-gated chloride channels. This overstimulation leads to rapid paralysis and death of the parasites. Because the medication is absorbed into the dog's bloodstream, it reaches fleas and ticks when they bite the dog, making it effective even before the parasites lay eggs.

Speed of Action and Efficacy

Afoxolaner is absorbed quickly after oral administration. Peak blood concentrations occur within 2 to 4 hours, and flea kill begins within 30 minutes. In clinical studies, NexGard demonstrated over 99% efficacy against adult fleas within 12 hours and maintained high efficacy against several tick species, including the brown dog tick, American dog tick, lone star tick, and black-legged tick (deer tick). Monthly dosing ensures continuous protection throughout the flea season.

Dosage and Administration

NexGard is available in four chewable sizes based on your dog's weight:

  • 4.1 to 10 lbs (1.8 to 4.5 kg)
  • 10.1 to 24 lbs (4.6 to 10.9 kg)
  • 24.1 to 60 lbs (10.9 to 27.2 kg)
  • 60.1 to 120 lbs (27.3 to 54.4 kg)

The chewable is palatable and usually accepted by dogs as a treat. It can be given with or without food, though offering it with a meal may help reduce the chance of gastrointestinal upset. Administer one chewable once a month on the same date each month for consistent protection.

What to Do If You Miss a Dose

If you miss a scheduled dose, give the missed chewable as soon as you remember. Then resume the regular monthly schedule. Do not give two doses within the same month. NexGard's efficacy may be reduced if the interval between doses exceeds 30 days, so set a reminder to stay on track.

Safety and Side Effects

NexGard is generally safe for dogs 8 weeks of age and older, weighing at least 4 pounds. It has been evaluated in breeding, pregnant, and lactating dogs with no adverse effects noted in studies, but always consult your veterinarian before using any medication in these populations.

Most dogs tolerate NexGard well. The most commonly reported side effects include vomiting, itching, lethargy, diarrhea, and decreased appetite. These effects are typically mild and self-limiting. As with any isoxazoline, there is a potential for neurologic reactions, including seizures, particularly in dogs with a history of seizure disorders. Use NexGard with caution in dogs with known epilepsy or seizures, and discuss your dog's medical history thoroughly with your veterinarian.

If your dog experiences severe vomiting, persistent diarrhea, or any neurologic signs (tremors, unsteadiness, seizures), discontinue use and contact your veterinarian immediately.

What to Expect at the Vet

NexGard is available only by prescription. Your veterinarian will:

  • Weigh your dog to determine the correct dose size.
  • Review your dog's medical history, especially any history of seizures or allergies.
  • Confirm your dog is current on heartworm prevention (NexGard does not prevent heartworms; it is often used alongside a heartworm preventive).
  • Provide a prescription and possibly a starter dose from the clinic.

Most veterinary practices will sell NexGard directly or provide a written prescription for online pharmacies. Expect to discuss the parasite risks in your area and the best overall prevention plan for your dog.

Prevention Tips

For maximum protection:

  • Administer NexGard monthly throughout the year, even in colder months, as fleas and ticks can survive indoors and in mild climates.
  • Combine with a heartworm preventive, such as Heartgard Plus or Interceptor Plus, for comprehensive coverage.
  • Keep your dog's environment clean: vacuum carpets, wash bedding, and treat your yard if flea infestations occur.
  • After outdoor walks, especially in wooded or grassy areas, check your dog for ticks. NexGard kills ticks once they bite, but removing attached ticks can reduce the risk of disease transmission.
  • Maintain a schedule: set a monthly reminder on your phone or calendar to ensure no gaps in protection.

By understanding NexGard's role in your dog's health, you can confidently use this medication to keep your pet free from fleas and ticks year-round.