Credelio Quattro (lotilaner, moxidectin, praziquantel, pyrantel) and Simparica Trio (sarolaner, moxidectin, pyrantel) are the two most broadly labeled oral combination parasiticides for dogs in the United States. Both cover fleas, ticks, heartworm, roundworms, and hookworms in a single monthly chew. But the differences between them — tapeworm coverage, tick species, speed of tick kill, and MDR1 safety data — matter when choosing which product fits a specific dog.

This article compares them head-to-head using current FDA label claims (as of early 2026), published head-to-head studies, and manufacturer safety data. It is not a recommendation for one over the other — the right choice depends on the dog's parasite exposure, geography, health history, and what the veterinarian recommends.

Quick comparison

Tapeworm coverage: the clearest differentiator

The most clinically meaningful difference between these two products is how they handle tapeworms.

Credelio Quattro: direct tapeworm treatment and control

Credelio Quattro includes praziquantel as its fourth active ingredient, giving it direct label claims for treating and controlling three tapeworm species:

• Dipylidium caninum (flea tapeworm)
• Taenia pisiformis
• Echinococcus granulosus

This means Credelio Quattro kills existing adult tapeworm infections in the dog's intestine at the time of dosing — not just the fleas that transmit D. caninum.

Simparica Trio: indirect flea tapeworm prevention

Simparica Trio does not contain praziquantel. In April 2025, the FDA approved a new label indication for Simparica Trio: prevention of Dipylidium caninum infections as a direct result of killing Ctenocephalides felis vector fleas on the treated dog.

This is an important distinction: Simparica Trio prevents flea tapeworm by eliminating the flea vector before transmission occurs. It does not treat an existing D. caninum infection, and it does not cover Taenia or Echinococcus species.

Bottom line: If a dog hunts, scavenges, or has exposure to Taenia (from eating small mammals) or Echinococcus (endemic in some regions of the western U.S.), Credelio Quattro's praziquantel provides direct treatment that Simparica Trio cannot. For purely flea-spread D. caninum risk in an urban or suburban dog with good flea control, both products offer protection — but through different mechanisms.

Tick species coverage: where Simparica Trio is broader

Both products cover the four most commonly encountered tick species in the United States, plus the longhorned tick (added to both labels in 2025). But Simparica Trio carries an additional label claim for the Gulf Coast tick (Amblyomma maculatum).

The Gulf Coast tick is expanding its range from the southeastern and south-central U.S. and can transmit Hepatozoon americanum (American canine hepatozoonosis). For dogs in Gulf Coast tick-endemic areas (coastal states from Texas to Virginia, and increasingly into the Midwest), this is a relevant gap for Credelio Quattro.

Speed of tick kill: lotilaner vs sarolaner

A head-to-head study published in Parasites & Vectors (Reif et al., 2024) compared lotilaner (the active ingredient in Credelio, not Credelio Quattro) against sarolaner (Simparica Trio) and afoxolaner (NexGard) for speed of kill against lone star ticks. The study found that lotilaner killed lone star ticks approximately 2x faster than sarolaner and afoxolaner, based on time to statistical significance versus untreated controls.

Elanco has used this data to argue that the lotilaner in Credelio Quattro provides faster and more sustained tick kill throughout the monthly dosing period. Zoetis has not published a head-to-head comparison of the combination products themselves (Credelio Quattro vs Simparica Trio), and the speed-of-kill study was conducted with standalone Credelio (lotilaner only), not the four-ingredient combination. The combination products have not been directly compared in published speed-of-kill trials.

Ingredient profile and safety

Isoxazoline class warning

Both products contain an isoxazoline (lotilaner in Credelio Quattro; sarolaner in Simparica Trio). The FDA has issued a class-wide fact sheet noting that isoxazolines have been associated with neurologic adverse reactions including tremors, ataxia, and seizures, even in dogs without a history of seizure disorders. Both labels carry this warning. Dogs with a history of seizures or neurologic disorders should use isoxazoline products cautiously and under veterinary supervision.

MDR1 gene mutation safety

Both products use moxidectin for heartworm prevention, but at different doses:

• Credelio Quattro delivers moxidectin at 0.02 mg/kg (maximum labeled dose: 0.04 mg/kg)
• Simparica Trio delivers moxidectin at 0.024 mg/kg (maximum labeled dose: 0.048 mg/kg)

A review in Today's Veterinary Practice (2025) noted that Credelio Quattro was shown to be safe in collies with the MDR1 gene mutation at up to 5 times the labeled dose, with only mild dose-dependent effects that were also observed in normal beagles. NexGard PLUS showed similar MDR1 safety margins. Simparica Trio at 5 times the labeled dose produced mild and self-limiting signs including ataxia and muscle twitching.

The lower moxidectin dose in Credelio Quattro (40 µg/kg maximum vs 48 µg/kg for Simparica Trio) may contribute to the slightly wider safety margin in MDR1-affected dogs. Both products are considered safe at labeled doses in MDR1-positive dogs, but the safety margin differs.

Food requirement

Credelio Quattro must be administered with food to achieve proper absorption. Simparica Trio has no food requirement but can be given with food. For dogs that are difficult to dose, or for owners who occasionally forget the food pairing, Simparica Trio is more forgiving.

Minimum weight

Simparica Trio is labeled for dogs as small as 2.8 lb, while Credelio Quattro requires a minimum of 3.3 lb. For very small breed puppies (toy breeds under 3.3 lb at 8 weeks), Simparica Trio can be started earlier.

Recent label changes (2024–2025)

Both products have received multiple FDA label updates since their original approvals:

Credelio Quattro:

• October 2024: Original approval (fleas, ticks, heartworm, roundworms, hookworms, tapeworms)
• May 2025: Label updated to include additional hookworm species (A. caninum expansion)
• October 2025: Lyme disease prevention added; longhorned tick coverage added
• December 2025: Credelio Quattro-CA1 conditionally approved for New World screwworm treatment

Simparica Trio:

• February 2020: Original approval
• January 2025: Asian longhorned tick coverage added
• April 2025: Prevention of flea tapeworm (D. caninum) by killing vector fleas added

Both products now carry Lyme disease prevention claims via killing Ixodes scapularis ticks. Both cover the longhorned tick. The tapeworm and Gulf Coast tick differences remain the primary clinical distinctions.

Which dogs favor which product

Consider Credelio Quattro when:

• The dog has tapeworm exposure risk beyond flea transmission — hunting, scavenging, or living in an area with Echinococcus or Taenia endemicity
• The dog is an MDR1-positive herding breed and the veterinarian prefers the wider moxidectin safety margin
• The owner wants a meat-allergen-free chew (Credelio Quattro is formulated without common meat allergens)
• Speed of lone star tick kill is a priority in the dog's geographic area

Consider Simparica Trio when:

• The dog lives in or travels to Gulf Coast tick-endemic areas (southeastern and south-central U.S.)
• The dog weighs less than 3.3 lb at the time heartworm prevention needs to start
• Food-independent dosing is important for compliance
• The dog's veterinary practice has an established Simparica Trio protocol and is monitoring the dog on it successfully

Neither product covers:

• Whipworm (Trichuris vulpis) — neither product has a whipworm claim. Dogs with whipworm exposure need a separate product like Interceptor Plus or a milbemycin oxime-based preventive.
• Mites (demodex, sarcoptic, ear mites) — neither product is labeled for mite treatment, though both isoxazolines have some off-label use in demodex management.
• Mosquitoes — neither repels mosquitoes, the vectors for heartworm transmission. They prevent heartworm by killing larvae after mosquito bites occur.

Sources

• Elanco. Credelio Quattro product label. NADA 141-581. https://assets-us-01.kc-usercontent.com/e4748d51-2c24-00f7-fc54-65f3864ee8b1/c20b2b29-23d4-439d-b01b-072b3bc3e2cf/PROMO_WEB_104239As_PA104239X_W1b_WS.pdf
• Zoetis. Simparica Trio prescribing information. NADA 141-521. https://www.zoetisus.com/content/_assets/docs/vmips/package-inserts/simparica-trio-prescribing-information.pdf
• FDA Freedom of Information Summary. NADA 141-521 supplement (April 8, 2025). https://animaldrugsatfda.fda.gov/adafda/app/search/public/document/downloadFoi/16785
• Reif KE, et al. "Comparative speed of kill provided by lotilaner (Credelio), sarolaner (Simparica Trio), and afoxolaner (NexGard) to control Amblyomma americanum infestations on dogs." Parasites & Vectors 17, 313 (2024). https://pubmed.ncbi.nlm.nih.gov/
• Elanco press release (October 27, 2025). Label expansion for Credelio Quattro and Credelio — Lyme disease prevention and longhorned tick. https://investor.elanco.com/press-releases/press-releases-details/2025/Elanco-Announces-Expansion-of-Credelio-Quattro-lotilaner-moxidectin-praziquantel-and-pyrantel-chewable-tablets-and-Credelio-lotilaner-Labels-Offering-Protection-Against-Lyme-Disease-and-an-Emerging-Tick-Species/default.aspx
• Zoetis press release (April 14, 2025). Simparica Trio new indication for prevention of flea tapeworm. https://news.zoetis.com/press-releases/press-release-details/2025/FDA-Approves-New-Indication-for-Zoetis-Simparica-Trio-sarolaner-moxidectin-and-pyrantel-chewable-tablets-Now-the-First-and-Only-Canine-Parasiticide-to-Prevent-Flea-Tapeworm-Infections-by-Killing-Vector-Fleas---2025-RBw-Z5OTg9/default.aspx
• Today's Veterinary Practice. "What's New With Parasiticides for Dogs and Cats." https://todaysveterinarypractice.com/parasitology/parasiticides-for-dogs-and-cats/
• FDA CVM. "Fact Sheet: Pet Owners and Veterinarians About Potential Adverse Events Associated with Isoxazoline Flea and Tick Products." https://www.fda.gov/animal-veterinary/animal-health-literacy/fact-sheet-pet-owners-and-veterinarians-about-potential-adverse-events-associated-isoxazoline-flea
• FDA CVM (December 17, 2025). Conditional approval of Credelio Quattro-CA1 for New World screwworm. https://www.fda.gov/animal-veterinary/cvm-updates/fda-conditionally-approves-drug-treat-new-world-screwworm-dogs