A label-based comparison of NexGard Plus and Simparica Trio for dogs, including flea, tick, heartworm, intestinal worm, safety, and patient-fit differences.

NexGard Plus and Simparica Trio are prescription preventives, and the right choice depends on the individual dog, local parasite risk, heartworm testing, and medical history.

NexGard Plus and Simparica Trio are more similar than different. Both are monthly oral prescription chewables for dogs. Both combine an isoxazoline flea/tick drug with moxidectin for heartworm prevention and pyrantel for certain intestinal worms. Both require attention to heartworm testing, neurologic history, labeled age and weight, and reproductive status.

The practical differences are in the flea/tick molecule, minimum labeled weight, exact intestinal worm and tick claims, and how a clinic prefers to match product records to local parasite risk.

Quick comparison

Feature	NexGard Plus	Simparica Trio
Active ingredients	Afoxolaner, moxidectin, pyrantel	Sarolaner, moxidectin, pyrantel
Dosing rhythm	Monthly oral chew	Monthly oral chew
Labeled age	Dogs and puppies 8 weeks and older	Dogs and puppies 8 weeks and older
Labeled minimum weight	4 lb	2.8 lb
Heartworm prevention	Yes, Dirofilaria immitis	Yes, Dirofilaria immitis
Fleas	Kills adult fleas; treats and prevents flea infestations	Kills adult fleas; treats and prevents flea infestations
Tick label	Black-legged, brown dog, American dog, lone star, Gulf Coast, longhorned ticks for one month	Lone star, Gulf Coast, American dog, black-legged, brown dog, Asian longhorned ticks for one month
Lyme-related label claim	Prevention of Borrelia burgdorferi infections as a direct result of killing Ixodes scapularis vector ticks	Same label claim
Roundworms	Toxocara canis and Toxascaris leonina	Immature adult/adult Toxocara canis and adult Toxascaris leonina
Hookworms	Adult Ancylostoma caninum, Ancylostoma braziliense, and Uncinaria stenocephala	L4, immature adult, and adult Ancylostoma caninum and adult Uncinaria stenocephala
Tapeworm-related claim	No comparable flea-vector tapeworm prevention claim in the indication section reviewed	Prevention of Dipylidium caninum infections as a direct result of killing flea vectors on the treated dog
Breeding/pregnancy/lactation	Safe use not evaluated	Safe use not evaluated

How vets think about the choice

For many healthy adult dogs, either product may be clinically reasonable if the dog's heartworm test is current and the label fits. The decision often turns on practical details:

Does the dog weigh less than 4 lb but at least 2.8 lb and meet the age minimum? Simparica Trio has the lower labeled minimum weight.
Is the clinic prioritizing a specific flea/tick molecule based on formulary, patient history, or owner experience?
Is the dog in a household where the Simparica Trio label's flea-vector Dipylidium caninum prevention claim is especially relevant?
Is the veterinarian focused on particular hookworm species or life stages based on fecal testing and local resistance concerns?
Which chew the dog will reliably take matters, because missed doses can defeat an otherwise strong plan.

This is not a ranking. It is a fit decision.

Shared safety issues

Both products contain an isoxazoline: afoxolaner in NexGard Plus and sarolaner in Simparica Trio. FDA's isoxazoline fact sheet says this class has been associated with neurologic adverse reactions including tremors, ataxia, and seizures in some dogs and cats, while noting the products can be safely used in many animals. Both labels advise caution in dogs with a history of seizures or neurologic disorders.

Both products include heartworm prevention. The labels say dogs should be tested for existing heartworm infection before administration, and neither product is effective against adult D. immitis. This is why a clinic may decline refills when a heartworm test is overdue or when doses have been missed.

Both labels say safe use has not been evaluated in breeding, pregnant, or lactating dogs. That should trigger a veterinarian conversation rather than an assumption that all monthly preventives are interchangeable.

Which product fits which dog?

Dog or household situation	Product direction to discuss
Very small puppy meeting age minimum but under 4 lb	Ask whether Simparica Trio's lower labeled minimum weight is relevant.
Dog with black-legged tick exposure in a Lyme-risk region	Ask about tick species, Lyme vaccination, tick checks, and the shared Borrelia-related label claim.
Dog with seizure history	Ask whether either isoxazoline product is appropriate or whether a different flea/tick strategy is safer.
Dog with repeated hookworm-positive fecal tests	Ask which hookworm species/stages are suspected and whether diagnostics or additional treatment are needed.
Owner misses separate products	Either combination chew may improve adherence if the dog takes it reliably.
Pregnant, lactating, or breeding dog	Ask for a reproductive-status-specific plan because safe use has not been evaluated on either label.

What not to do

Do not give both products together unless a veterinarian specifically instructs you to do so. They overlap heavily. Do not switch after a missed dose without telling the clinic the exact timing. Do not buy foreign-market products with similar names and assume the U.S. label applies. Do not use dog products in cats.

If your dog vomits, refuses the chew, eats another dog's chew, develops tremors or wobbliness, has a seizure, collapses, or has facial swelling or breathing trouble, contact a veterinarian immediately. Severe neurologic signs, collapse, pale gums, or respiratory distress are emergencies.

Bottom line

NexGard Plus and Simparica Trio are both broad monthly dog preventives. NexGard Plus may stand out when its adult Ancylostoma braziliense hookworm claim matters. Simparica Trio may stand out for smaller eligible puppies, the specific hookworm life-stage language on its label, or its flea-vector Dipylidium caninum prevention claim. For most dogs, the deciding factor is a veterinarian's assessment of risk, history, testing, and adherence.

For full product pages, see NexGard Plus for Dogs and Simparica Trio for Dogs. For prevention strategy beyond these two products, see Dog Heartworm Prevention.