NexGard PLUS vs Simparica Trio: Which Is Better for Your Dog?

Introduction

Both NexGard PLUS and Simparica Trio are monthly all-in-one chewables. Both require a prescription. Both cover fleas, ticks, heartworm, roundworms, and hookworms. So when dog owners ask about NexGard PLUS vs Simparica Trio, the answer shouldn’t be “they’re basically the same” — because they’re not.

The real differences come down to how fast each product kills ticks, which specific parasites each one covers, how small a dog can safely take it, and what you’ll actually pay at the pharmacy. For a dog in the Northeast hiking through tick country, the 8-hour vs 24-hour tick kill difference is not a minor detail. For a 3-pound Chihuahua puppy, only one of these products is even an option.

If you’re here because your vet mentioned both and you want to know which to ask about — that’s exactly what this article covers.

For most dogs and most dog owners, Simparica Trio edges out NexGard PLUS — but there are specific situations where NexGard PLUS is the smarter call.

NexGard PLUS vs Simparica Trio: What’s Actually Different?

At first glance, these two products look nearly identical. Both are beef- or liver-flavored soft chews. Both are given once a month. Both combine three active ingredients: one isoxazoline for fleas and ticks, moxidectin for heartworm prevention, and pyrantel for intestinal worms.

The shared ingredients — moxidectin and pyrantel — are functionally identical across both products at the same dose of pyrantel. The difference that matters is the isoxazoline compound. NexGard PLUS uses afoxolaner. Simparica Trio uses sarolaner. Both work by disrupting the nervous system of fleas and ticks, causing paralysis and death. But sarolaner acts faster on ticks — within 8 hours vs approximately 24 hours for afoxolaner against black-legged ticks.

Why does 8 hours vs 24 hours matter? The bacteria that causes Lyme disease (Borrelia burgdorferi) typically needs 24 to 48 hours of continuous tick attachment to transmit from a tick to your dog. Simparica Trio’s 8-hour kill window closes that transmission window much tighter than NexGard PLUS’s 24-hour window. For dogs in tick-heavy regions, that is a real clinical difference — not marketing language.

There’s also a moxidectin dose difference worth knowing. NexGard PLUS delivers moxidectin at 12 mcg/kg. Simparica Trio delivers it at 24 mcg/kg — double the dose. For most dogs, this doesn’t matter. For herding breeds with the MDR1 gene mutation (Collies, Australian Shepherds, Shelties), the lower dose in NexGard PLUS gives a slightly wider margin of safety.

One more update: in April 2025, the FDA approved a new label claim for Simparica Trio — it’s now the only combination parasiticide that prevents flea tapeworm infections (Dipylidium caninum) by killing the vector fleas. NexGard PLUS does not have this claim.

What Does Each Product Actually Cover?

This is where most comparison articles get it wrong — especially ones written before 2025. Both products have had label updates in the last two years that changed the coverage picture significantly.

Tick Coverage — Updated for 2025

Both NexGard PLUS and Simparica Trio now cover six U.S. tick species: the black-legged tick (Ixodes scapularis), American dog tick (Dermacentor variabilis), lone star tick (Amblyomma americanum), brown dog tick (Rhipicephalus sanguineus), Gulf Coast tick (Amblyomma maculatum), and Asian longhorned tick (Haemaphysalis longicornis).

Both also now carry an FDA-labeled claim for preventing Lyme disease infections as a direct result of killing black-legged ticks. If you’ve read an article saying that NexGard PLUS lacks Gulf Coast tick or Lyme disease coverage — that information is outdated.

The real tick differentiator isn’t which ticks they cover. It’s how fast. Simparica Trio starts killing black-legged ticks within 8 hours. NexGard PLUS takes approximately 24 hours. Given that Borrelia burgdorferi typically requires 24 to 48 hours of tick attachment to transmit, Simparica Trio’s speed advantage is clinically meaningful for dogs spending time in Lyme-endemic areas — the Northeast, mid-Atlantic, Great Lakes, and upper Midwest.

Intestinal Worm Differences

Both products cover two roundworm species (Toxocara canis and Toxascaris leonina) and at least two hookworm species. Here’s where they diverge.

NexGard PLUS covers three hookworm species, including Ancylostoma braziliense — a hookworm more commonly found in subtropical regions of the U.S. (Florida, coastal Gulf states, Hawaii). Simparica Trio covers two hookworm species and skips A. braziliense.

Simparica Trio counters with its new flea tapeworm prevention claim. By killing the flea vector before transmission, it prevents Dipylidium caninum infections — something NexGard PLUS is not labeled to do. Neither product covers whipworms or sarcoptic mange. If those are concerns for your dog, your vet will need to add a separate product.

Heartworm Prevention

Both products use moxidectin for heartworm prevention and both perform essentially identically in efficacy studies. A 2024 Parasites & Vectors study found NexGard PLUS was 99.5% effective and Simparica Trio was 99.8% effective against heartworm larvae — a difference that’s statistically negligible for practical purposes.

Before starting either product, your dog must be tested for existing heartworm infection. Neither product treats adult heartworms — they only prevent new infections from developing. Starting a preventive in a heartworm-positive dog can trigger a serious reaction. This is a conversation for your vet, not a self-assessment. [INTERNAL: heartworm prevention for dogs guide]

Skipping even one monthly dose creates a gap in protection. If you miss a dose, give it as soon as you remember and resume your monthly schedule.

NexGard PLUS vs Simparica Trio Cost: What You’ll Actually Pay

Pricing varies by dog weight. Here’s what you’ll pay on Chewy Rx for a 6-pack (6-month supply) as of May 2026.

The monthly price difference is modest — roughly $2 to $4 per month at mid-to-large sizes. But there are two money factors that tip the balance further toward Simparica Trio.

The $40 Simparica Trio rebate. Zoetis is currently offering $40 in Petcare Rewards for first-time 6-pack purchases, valid through October 31, 2026. That essentially wipes out most of the price difference in year one and then some. Check the Zoetis Petcare Rewards program directly or ask your vet’s office.

The 100% satisfaction guarantee. Zoetis backs Simparica Trio with a satisfaction guarantee on protection. NexGard PLUS does not currently offer this.

One smart move that many owners miss: ask your vet for a written take-home prescription instead of filling it in the clinic. You’re legally entitled to one in every U.S. state, and Chewy Rx consistently prices both products lower than vet-clinic dispensing rates.

Simparica Trio or NexGard PLUS: Which Should You Ask Your Vet About?

The right answer depends on your dog specifically — their size, where you live, their breed, and what parasites are actually a risk in your area. Here’s a framework that cuts through the noise.

Your dog weighs less than 4 lbs

Choose Simparica Trio — there is no choice to make. NexGard PLUS requires a minimum weight of 4 lbs. Simparica Trio is FDA-approved down to 2.8 lbs. For Chihuahuas, Yorkies, Maltese, and toy breed puppies in that 2.8–3.9 lb window, Simparica Trio is the only option in this category. Ask your vet to confirm the correct weight tier before starting.

You live in a Lyme-endemic or high-tick area

Choose Simparica Trio. The Northeast, mid-Atlantic, Great Lakes region, and upper Midwest all have high black-legged tick populations and elevated Lyme disease risk. Simparica Trio kills those ticks within 8 hours — before the Lyme-causing bacteria has enough time to transmit. NexGard PLUS takes approximately 24 hours. For a dog regularly walking trails or running through grass in these regions, that speed difference is worth paying attention to.

You have a herding breed — Collie, Australian Shepherd, Sheltie, Border Collie

Ask your vet specifically about NexGard PLUS. Both products have been evaluated in MDR1-deficient dogs and are considered safe at labeled doses. However, NexGard PLUS showed no serious adverse effects at up to 5 times the labeled dose in MDR1-sensitive dogs. Simparica Trio was safe up to 3 times the labeled dose, with mild self-limiting signs at 5 times. Neither should be avoided based on breed alone — but the wider NexGard PLUS safety margin is worth bringing up with your vet if your dog has a confirmed MDR1 mutation.

You want the most complete all-in-one protection

Choose Simparica Trio. It’s the only combination parasiticide with an FDA-approved claim for preventing flea tapeworm infections (Dipylidium caninum). For dogs who attend daycare, visit dog parks, live in multi-pet households, or spend significant time outdoors, this extra layer of coverage is genuinely useful. NexGard PLUS offers broader hookworm coverage (three species vs two), which matters mainly in subtropical U.S. regions where Ancylostoma braziliense is present — Florida, the Gulf Coast, and Hawaii.

If your dog is primarily indoors, lives in a low-heartworm-risk region, and is already on a dedicated flea and tick product that’s working, switching to a combo product may not be necessary. That’s worth discussing with your vet at the next annual visit — not a decision to make based on an online article alone.

Side Effects: What to Watch For After Giving Either Product

Both NexGard PLUS and Simparica Trio carry the FDA’s isoxazoline class warning for potential neurologic adverse events. This is not a recall. It’s a class-wide label requirement that applies to every product in this drug class — Bravecto, Credelio, NexGard, and Simparica included. The FDA continues to consider both products safe and effective for the majority of dogs.

Most common side effects (both products):

• Vomiting and diarrhea are the most frequently reported side effects in clinical trials for both products. These are typically mild and resolve on their own within 24 to 48 hours. Giving either chew with a small meal significantly reduces the chance of stomach upset.
• NexGard PLUS clinical trials also commonly reported lethargy and itching as adverse reactions, in addition to vomiting and diarrhea. These were generally mild and self-limiting in study animals.
• Simparica Trio clinical trials additionally noted lethargy, decreased appetite, increased urination, hyperactivity, and increased thirst in field studies — though vomiting and diarrhea remained the primary findings.

Neurologic adverse events (rare but real):

Muscle tremors, an unsteady gait (ataxia), and seizures have been reported with isoxazoline-class products. These events are rare, but they can occur even in dogs with no prior seizure history. If your dog has a history of seizures or any neurologic condition, consult your vet before starting either product. Monitor your dog for the first 24 hours after the initial dose.

MDR1-sensitive breeds:

Breeds that commonly carry the MDR1/ABCB1 gene mutation — Collies, Australian Shepherds, Shetland Sheepdogs, Border Collies, and related herding breeds — can be more sensitive to certain drug compounds. Both NexGard PLUS and Simparica Trio have been tested in MDR1-affected dogs and are considered safe at labeled doses. NexGard PLUS was evaluated as safe at up to 5 times the labeled dose in MDR1-deficient Collies. Simparica Trio was safe up to 3 times the labeled dose, with mild and self-limiting signs observed at 5 times. Affordable genetic testing for the MDR1 mutation is available through Washington State University’s Veterinary Clinical Pharmacology Lab — worth considering before starting any macrocyclic lactone-containing product in a herding breed.

If anything seems off after giving either product — unusual stumbling, persistent vomiting, muscle twitching — contact your vet. These events are uncommon but not zero.

Frequently Asked Questions

Our Verdict: NexGard PLUS vs Simparica Trio

Simparica Trio is the better choice for most dogs.

Three reasons stand out. First, it kills ticks faster — 8 hours vs approximately 24 hours — which is a real advantage in any Lyme-endemic region. Second, it’s the only combination parasiticide with FDA approval to prevent flea tapeworm infections as of April 2025. Third, it costs slightly less per month and comes with an active $40 rebate through October 2026 that makes the price gap even wider in year one.

NexGard PLUS makes more sense in three specific situations: you have a herding breed with a confirmed MDR1 mutation and want the wider tested safety margin, your dog lives in a subtropical region (Florida, Gulf Coast, Hawaii) where Ancylostoma braziliense hookworm coverage matters, or your dog is a stubborn beef-flavor holdout who won’t touch liver. NexGard PLUS’s 96.3% acceptance rate vs Simparica Trio’s 91.9% is a real difference if you’re dealing with a picky dog.

For everyone else — especially dogs in tick-prone areas or households that want the most complete single-chew protection available — Simparica Trio is the one to bring up with your vet.

We update this article every 90 days as pricing, rebate programs, and FDA label changes occur.

Veterinary Disclaimer: This article is for informational purposes only and does not constitute veterinary advice. NexGard PLUS and Simparica Trio are prescription medications. Always consult your licensed veterinarian before starting, stopping, or switching any parasite prevention program. Dogs must be tested for heartworm infection before starting either product.