Medication Guide • Reviewed by Dr. Tiffany Delacruz, DVM
NexGard for Dogs
NexGard is a monthly beef-flavored chewable that kills fleas and ticks in dogs. NexGard PLUS adds heartworm and intestinal worm coverage.
What NexGard is used for in dogs
- Monthly flea prevention
- Tick prevention (including ticks that carry Lyme disease)
- Heartworm prevention (NexGard PLUS)
- Roundworm and hookworm control (NexGard PLUS)
How it works
Afoxolaner blocks parasite nerve receptors, killing fleas within 8 hours and most tick species within 24-48 hours of biting.
Available formulations
Beef-flavored chewable, monthly
NexGard PLUS combo
Side effects to know
Common side effects
- • Mild vomiting
- • Lethargy after first dose
These usually resolve on their own. If they persist past the first few doses, ask your vet.
Call your vet immediately if you see
- ⚠ Neurologic signs (tremors, ataxia, seizures — rare)
- ⚠ Severe lethargy
Drug interactions
- • Consult your vet if your dog takes seizure medications
When not to use
- • Puppies under 8 weeks or 4 lbs
- • Dogs with seizure history (use cautiously)
- • Dogs with documented isoxazoline sensitivity
Monitoring during treatment
First-time use should be observed for 24 hours, especially in small dogs.
Need a NexGard refill?
RexVet is the first 501(c)(3) non-profit online vet service in the U.S. Talk to a licensed veterinarian by video, get your dogs's NexGard prescription, and have it shipped through RexVetRx — all for $64.99 per visit.
Book a vet visit — $64.99NexGard for Dogs
Frequently asked questions
How long does NexGard last?
Each chewable provides a full 30 days of flea and tick protection. Give monthly on the same day for consistent coverage.
Can I give NexGard with food?
Yes — it can be given with or without food. The flavored chewable is well-accepted by most dogs.
NexGard vs Simparica?
Both are isoxazolines, both are oral monthly chewables, both kill fleas and most ticks. NexGard PLUS and Simparica TRIO are the comparable combo products. Your vet can help choose based on availability and price.
Can RexVet prescribe NexGard?
Yes. A quick RexVet video visit (with a current heartworm test for the PLUS combo) and we ship monthly through RexVetRx.
What if my dog vomits after NexGard?
If within 2 hours, call your vet — they may recommend repeating the dose. After 2 hours, the dose was likely absorbed.
Medical review by Dr. Tiffany Delacruz, DVM
Chief Executive Officer & Lead Veterinarian, RexVet. Licensed in Florida, New York, and Virginia.
Last fact-checked: 2026-05-19
Sources
This page is an educational reference and does not replace veterinary advice. Always consult a licensed veterinarian before starting, changing, or stopping medication for your pet.