NexGard vs Simparica Trio: which is best for your dog?
Key Takeaways
- NexGard and Simparica Trio cover the same fleas and the same six tick species.
- Simparica Trio also provides heartworm prevention plus treatment for roundworm and hookworm.
- NexGard is labeled for dogs 8 weeks and older weighing 4 lb or more, while Simparica Trio starts lower at 2.8 lb.
- Both medications are isoxazoline-class chews; talk to your vet if your dog has a history of seizures.
Short Answer
NexGard and Simparica Trio protect against the same fleas and the same six tick species, and both are FDA-approved to help prevent Lyme disease. Simparica Trio also prevents heartworm and treats roundworms and hookworms, while NexGard only covers fleas and ticks. If your dog isn't already on a heartworm preventive, Simparica Trio covers more in one chew; if heartworm is handled separately, NexGard may be all you need.
Keeping your dog protected from fleas, ticks, and other parasites is one of those responsibilities that feels straightforward until you start comparing products. Take NexGard and Simparica Trio. They look similar on the shelf, but they cover different ground. This guide breaks down what sets them apart, so you can feel confident about which one is right for your dog.
Two chews can look similar while covering very different parasites. I recommend comparing the exact label claims, not just the product category, so heartworm or intestinal-parasite coverage is not assumed.
Dr. Sean Ellison, DVM
At a glance: NexGard vs. Simparica Trio
This guide compares original NexGard, the flea and tick chew, with Simparica Trio. It does not cover NexGard PLUS or NexGard Spectra, which add heartworm and intestinal worm protection of their own. If you're weighing an all-in-one NexGard against Simparica Trio, NexGard PLUS is the closer comparison, and your vet can point you to the right one.
The headline difference is scope. NexGard stays in the flea and tick lane, while Simparica Trio adds heartworm prevention plus treatment for two common intestinal worms in one chew. Both products' FDA-approved labels confirm this split.
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What parasites does each medication protect against?
Two products are not interchangeable. NexGard is built to handle external parasites. It's a monthly beef-flavored chewable that starts working quickly, killing adult fleas before they can lay eggs and helping stop an infestation from taking hold.
On the tick side, NexGard is approved to treat and control six species: the black-legged tick (also called the deer tick), the American dog tick, the lone star tick, the Gulf Coast tick, the brown dog tick, and the Asian longhorned tick. Because it kills black-legged ticks, NexGard is FDA-approved to help prevent infections that can cause Lyme disease.
Standard NexGard does not prevent heartworm disease or treat intestinal worms. Its FDA label covers only fleas, ticks, and Lyme prevention. So if you give NexGard on its own, you'll still need a separate heartworm and worming product for more complete coverage. If your primary worry is fleas and ticks, NexGard covers it. If you want more, you'll be adding a second medication. For a broader look at how NexGard stacks up against other flea and tick options, our guide to the 11 best flea and tick meds for dogs walks through the choices.
Simparica Trio: all-in-one protection
Simparica Trio takes a wider approach. A single monthly liver-flavored chew covers fleas, ticks, heartworm, and intestinal worms, which is why it's one of the most commonly prescribed preventives at Dutch. You can see it on the Dutch pharmacy page for Simparica Trio.
Its coverage includes:
- The same six ticks NexGard covers: the deer tick, American dog tick, lone star tick, Gulf Coast tick, brown dog tick, and Asian longhorned tick.
- Heartworm disease, a potentially fatal condition spread by mosquitoes.
- Roundworms and hookworms, two common intestinal parasites.
Like NexGard, Simparica Trio is FDA-approved to block infections that may cause Lyme disease by killing deer ticks. For dogs already on the standard flea-and-tick version of Simparica, our Simparica vs. Simparica Trio comparison explains what the "Trio" adds.
Note: Simparica Trio treats roundworms and hookworms, and it helps prevent tapeworm infections by killing the fleas that carry them. It does not cover whipworms, and it won't clear a tapeworm infection your dog already has. If whipworms are a concern in your area, talk with a vet.
Active ingredients and how they work
NexGard relies on a single ingredient: afoxolaner. It targets the nervous systems of fleas and ticks, causing overstimulation that kills them quickly after they bite your dog.
Simparica Trio uses three ingredients, each with its own job:
- Sarolaner works much like afoxolaner by targeting the nervous systems of fleas and ticks.
- Moxidectin prevents heartworm disease.
- Pyrantel is a dewormer that treats and controls roundworms and hookworms.
That three-ingredient design is what lets Simparica Trio do in one chew what would otherwise take two or three separate products.
Key differences to consider
Beyond the ingredient list, a few practical factors will determine which product best fits your dog.
Spectrum of coverage
This is the core of the decision. NexGard and Simparica Trio cover the same fleas and the same six tick species. Simparica Trio adds heartworm prevention and intestinal worm treatment on top of that shared flea and tick coverage. The added heartworm and worm protection is the difference, not ticks. If you want the full picture on year-round protection options, our roundup of the best flea and tick prevention for dogs in 2026 gives more context.
Dog age and weight requirements
For owners of very small dogs, this can be the deciding factor.
- NexGard: for dogs and puppies 8 weeks of age and older, weighing 4 pounds or more.
- Simparica Trio: for dogs and puppies 8 weeks of age and older, weighing 2.8 pounds or more.
Per the products' labels, Simparica Trio starts at 2.8 lbs while the NexGard line starts at 4 lbs, so Simparica Trio is the better fit for extra-small dogs. If you have a toy breed puppy who hasn't hit 4 pounds yet, Simparica Trio may be the only one of the two your dog is eligible for.
Total cost of protection
This is where comparing sticker prices gets misleading. A box of NexGard often costs less than a box of Simparica Trio, so NexGard can look like the budget-friendly pick.
A dog on original NexGard still needs a separate heartworm preventive; the need for additional intestinal-parasite treatment should be based on fecal testing, exposure risk, and veterinary guidance.
The true comparison would be NexGard plus a heartworm product versus Simparica Trio alone. Once you add the second medication, the "more affordable" option often isn't more affordable at all.
You can compare pricing directly on the Dutch Vet pharmacy page. When you're weighing the full cost of keeping your dog protected, the all-in-one route is often the more economical one.
Isoxazolines are safe and effective for many dogs, but a seizure or neurologic history belongs in the product-selection conversation. The goal is to balance parasite risk with the individual dog's medical history.
Dr. Sean Ellison, DVM
Are NexGard and Simparica Trio safe?
Both medications are FDA-approved and considered safe and effective for most dogs when used as directed. The most commonly reported side effects are mild, such as vomiting, diarrhea, lethargy, or changes in appetite. Most dogs take these chews without any issue.
Afoxolaner and sarolaner belong to a group of drugs called the isoxazoline class. The FDA requires isoxazoline-class flea and tick products to carry a warning about the potential for neurologic side effects, including muscle tremors and seizures. These reactions are uncommon, and many dogs with no history of neurologic problems take these medications for years without trouble.
The warning matters most for dogs with a pre-existing history of seizures or other neurologic conditions. If that describes your dog, talk with a veterinarian before starting either product. A vet can review your dog's health history and help you weigh whether an isoxazoline-based preventive is the right fit or whether a different type of prevention makes more sense.
How to choose the right parasite protection for your dog
Here's a simple way to apply everything above to your situation.
Choose NexGard if:
- Your main concern is fleas and ticks.
- Your dog is already on a separate heartworm preventive (like Heartgard Plus) that you and your vet are happy with, so you're really just adding flea and tick coverage.
Choose Simparica Trio if:
- You want one chew that covers fleas, ticks, heartworm, roundworms, and hookworms.
- You'd rather simplify your dog's monthly routine and not juggle multiple products.
- Your dog isn't currently on a heartworm preventive.
- Your dog weighs at least 2.8 pounds but under 4 pounds, which rules out NexGard.
For most dogs who aren't already on heartworm prevention, Simparica Trio's all-in-one approach is the more complete and often more cost-effective choice.
A quick word on year-round prevention
You might wonder whether parasite prevention is a seasonal thing you can pause in winter. Both the American Heartworm Society and the Companion Animal Parasite Council recommend year-round prevention regardless of season. Mosquitoes, fleas, and ticks can survive indoors and in milder climates well outside the warm months, and heartworm-resistant strains are especially prevalent in some regions, like the Mississippi Delta. Consistent, year-round coverage is the safest bet. Our guide to intestinal worms and parasites in dogs covers the why in more detail.
Get the right prescription with Dutch
Both NexGard and Simparica Trio are prescription medications, which means a licensed veterinarian needs to establish a relationship with your dog before either can be prescribed. That relationship, called a veterinarian-client-patient relationship, or VCPR, can be established remotely through telehealth in most states.
With Dutch, you can have a video consult with a licensed vet to talk through your dog's weight, age, health history, and lifestyle, then get a prescription for the option that fits. If your dog is a good candidate, the medication ships directly to your door at a competitive price, with free standard shipping and faster options available. A Dutch membership covers up to five pets and costs less than a single typical vet visit, making it easier for multi-dog households to stay on top of prevention.
Dutch complements the care your local vet provides. For hands-on exams, lab work, and anything urgent, in-person care is still essential. But for choosing and refilling a routine parasite preventive, a virtual consult can save you a trip while still bringing the same expertise you'd expect at a clinic.
Choosing the right parasite protection
The right choice comes down to two questions: Is your dog already covered for heartworm, and how simple do you want your routine to be? NexGard offers solid flea and tick coverage, while Simparica Trio bundles heartworm and intestinal worm protection into a single monthly chew, which often makes it the smarter total-cost option.
If your dog needs broader protection or you want to ask about getting oral flea medication without a vet office visit, a Dutch vet can help you review options in a video consult and, in most states, send a prescription directly to your door.
If you are unsure which medication is best for your dog, talk to a vet at Dutch.
Talk to a vet at Dutch about your dog's flea and tick protection today.
- 24/7 care from top-rated vets
- Unlimited vet calls & messaging
About the Reviewer
Dr. Sean Ellison, DVM, is a University of Wisconsin-Madison graduate with 22 years of experience in veterinary care. His areas of interest include nutrition, internal medicine, hospice, and palliative care. He enjoys providing veterinary services to communities that may not have ready access to traditional in-person care.
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