Simparica Trio is an all-in-one monthly chewable parasiticide for dogs manufactured by Zoetis. It combines three active ingredients — sarolaner, moxidectin, and pyrantel pamoate — to provide comprehensive protection against fleas, ticks, heartworm disease, roundworms, and hookworms in a single tablet. This broad spectrum of coverage has made Simparica Trio one of the most popular parasite prevention products on the market. It is FDA-approved for dogs and puppies 8 weeks of age or older weighing at least 2.8 pounds and requires a veterinary prescription.
What Is Simparica Trio Used For?
Simparica Trio provides monthly protection against five major parasite threats:
- Fleas — kills adult fleas (Ctenocephalides felis) and is indicated for the treatment and prevention of flea infestations
- Ticks — kills five species of ticks:
- Black-legged tick (deer tick, Ixodes scapularis)
- American dog tick (Dermacentor variabilis)
- Lone Star tick (Amblyomma americanum)
- Brown dog tick (Rhipicephalus sanguineus)
- Gulf Coast tick (Amblyomma maculatum)
- Heartworm disease — prevents heartworm disease caused by Dirofilaria immitis
- Roundworms — treats and controls roundworm infections (Toxocara canis, Toxascaris leonina)
- Hookworms — treats and controls hookworm infections (Ancylostoma caninum, Uncinaria stenocephala)
Additionally, Simparica Trio has been shown in studies to help prevent Borrelia burgdorferi infections transmitted by ticks, which is relevant to Lyme disease prevention.
How Does Simparica Trio Work?
Simparica Trio contains three active ingredients, each targeting different parasites:
Sarolaner (isoxazoline) targets fleas and ticks by inhibiting ligand-gated chloride channels (GABA and glutamate-gated) in the parasites’ nervous systems. This causes uncontrolled nerve activity, paralysis, and death. Sarolaner is absorbed into the dog’s bloodstream after ingestion and kills parasites when they bite and feed.
Moxidectin (macrocyclic lactone) prevents heartworm disease by killing heartworm larvae (microfilariae and L3/L4 stage larvae) before they can mature into adult worms. Moxidectin also works through chloride channel disruption, but it targets the specific channels found in nematode (worm) nervous systems.
Pyrantel pamoate (tetrahydropyrimidine) treats intestinal roundworms and hookworms by causing spastic paralysis of the worms, which are then expelled from the gastrointestinal tract. Pyrantel acts as a depolarizing neuromuscular blocking agent in susceptible parasites.
Dosage
Simparica Trio is dosed by weight and given once monthly. Your veterinarian will prescribe the correct tablet size for your dog. Do not split tablets.
| Dog’s Weight | Sarolaner | Moxidectin | Pyrantel (as pamoate salt) | Tablet Color |
|---|---|---|---|---|
| 2.8 - 5.5 lbs (1.25 - 2.5 kg) | 3 mg | 0.06 mg | 12.5 mg | Gold |
| 5.6 - 11.0 lbs (2.6 - 5.0 kg) | 6 mg | 0.12 mg | 25 mg | Purple |
| 11.1 - 22.0 lbs (5.1 - 10.0 kg) | 12 mg | 0.24 mg | 50 mg | Caramel |
| 22.1 - 44.0 lbs (10.1 - 20.0 kg) | 24 mg | 0.48 mg | 100 mg | Tan |
| 44.1 - 88.0 lbs (20.1 - 40.0 kg) | 48 mg | 0.96 mg | 200 mg | Green |
| 88.1 - 132.0 lbs (40.1 - 60.0 kg) | 72 mg | 1.44 mg | 300 mg | Brown |
For dogs over 132 lbs, use the appropriate combination of tablets as directed by your veterinarian. Administer every 30 days, year-round in most regions.
Important: A heartworm test is recommended before starting any heartworm prevention medication. Starting prevention in a dog that is already infected with heartworms may cause harmful reactions. Your veterinarian will test your dog and establish an appropriate prevention schedule.
How to Give Simparica Trio to Your Dog
- Simparica Trio is a liver-flavored chewable tablet designed for palatability.
- Offer the tablet as a treat or give it with food. Ensure your dog chews the tablet completely rather than swallowing whole.
- If your dog vomits within an hour of dosing, re-dose with another full tablet and consult your veterinarian.
- Administer on the same date each month for uninterrupted protection.
- If you miss a dose, give it as soon as you remember and resume the monthly schedule from that date.
- Begin use only after your veterinarian has confirmed a negative heartworm test.
Side Effects
| Common Side Effects | Serious Side Effects (Contact Your Vet) |
|---|---|
| Vomiting | Seizures |
| Diarrhea | Tremors or muscle twitching |
| Lethargy | Ataxia (uncoordinated movement) |
| Decreased appetite | Severe or persistent vomiting/diarrhea |
| Signs of allergic reaction (swelling, hives, difficulty breathing) |
FDA Isoxazoline Class Warning: All isoxazoline products (including sarolaner in Simparica Trio) carry an FDA class-wide label warning regarding potential neurologic adverse events, including seizures, tremors, and ataxia. These events have been reported in some animals, including those without a prior history of neurologic conditions. While uncommon, dogs with a history of seizures may be at increased risk. Discuss your dog’s full health history with your veterinarian.
Drug Interactions
- Other isoxazoline products (NexGard, Bravecto, Credelio): Do not use concurrently with other isoxazoline flea/tick products.
- Other heartworm preventatives: Do not double up on heartworm prevention unless specifically directed by your veterinarian.
- P-glycoprotein substrates: Moxidectin is a substrate for P-glycoprotein. Dogs with MDR1 gene mutations (see Contraindications) may have altered drug handling.
- Seizure medications: Dogs on anticonvulsant therapy should be carefully evaluated before starting any isoxazoline product.
Contraindications
- Dogs under 8 weeks of age or weighing less than 2.8 pounds
- Dogs with a known hypersensitivity to sarolaner, moxidectin, or pyrantel
- Dogs with a history of seizures should be carefully evaluated (risk-benefit discussion recommended)
- MDR1 gene mutation dogs: While the moxidectin dose in Simparica Trio is well below doses that cause toxicity in MDR1 dogs, inform your veterinarian if your dog is a Collie, Australian Shepherd, Shetland Sheepdog, or other herding breed, or is known to carry the MDR1 mutation
- Heartworm-positive dogs: A heartworm test should be performed before starting. Giving heartworm prevention to an already-infected dog may cause harmful reactions
- Breeding, pregnant, or lactating dogs: Safety not fully evaluated in these populations
Storage
- Store at 68-77degF (20-25degC).
- Excursions to 59-86degF (15-30degC) are permitted.
- Keep in original packaging until ready to use.
- Keep out of reach of children and other animals.
Cost & Availability
Simparica Trio is a prescription-only product with no generic available.
- Approximate cost (6-month supply, medium dog): $110-$160
- Per-month cost: $18-$27 per dose depending on dog size and retailer
- Available through veterinary clinics and licensed online pet pharmacies
- Manufacturer rebates are sometimes available — ask your veterinarian
Simparica Trio’s all-in-one coverage may reduce total monthly parasite prevention costs compared to purchasing separate flea/tick and heartworm products. Discuss the most cost-effective approach for your situation with your veterinarian.
Frequently Asked Questions
How does Simparica Trio compare to NexGard Plus? Both are monthly all-in-one chewable parasiticides covering fleas, ticks, heartworm, roundworms, and hookworms. Simparica Trio uses sarolaner + moxidectin + pyrantel, while NexGard Plus uses afoxolaner + moxidectin + pyrantel. Both carry the same isoxazoline class warning. The tick species coverage differs slightly between the two. Your veterinarian can help you decide which product is most appropriate for your dog based on local parasite risks and your dog’s health history.
Does Simparica Trio protect against tapeworms? No. Simparica Trio does not cover tapeworms. If tapeworm protection is desired, Credelio Quattro (which includes praziquantel) is currently the only isoxazoline combination product that covers tapeworms. Your veterinarian may prescribe a separate dewormer if tapeworms are a concern.
Do I still need a heartworm test if my dog is on Simparica Trio? Yes. The American Heartworm Society recommends regular heartworm testing even for dogs on consistent prevention. Testing confirms the preventative is working and detects any breakthrough infections. Your veterinarian will establish an appropriate testing schedule, typically annually.
Is Simparica Trio safe for Collies and herding breeds? The moxidectin component is a macrocyclic lactone, which can be of concern at high doses in dogs with the MDR1 gene mutation common in herding breeds. However, the moxidectin dose in Simparica Trio is substantially lower than doses associated with toxicity in MDR1-affected dogs. Consult your veterinarian, who can advise on MDR1 testing and the safety of this product for your specific dog.
When should I start my puppy on Simparica Trio? Simparica Trio is approved for puppies 8 weeks of age and older weighing at least 2.8 pounds. Your veterinarian will recommend when to begin based on your puppy’s age, weight, and local parasite risk. A heartworm test may be needed depending on age and exposure history.
Sources & References
- FDA - Simparica Trio Product Label
- FDA - Isoxazoline Flea and Tick Products Fact Sheet
- Merck Veterinary Manual - Heartworm Disease in Dogs
- VCA Hospitals - Heartworm Prevention
- American Heartworm Society - Current Guidelines
- Zoetis - Simparica Trio Product Information
Verification Notes
Simparica Trio’s ingredient composition, weight-based dosing, and parasite coverage are consistent with the FDA-approved product label. The heartworm testing recommendation aligns with the fact-check report (Claim C25), which notes the American Heartworm Society recommends testing before initiating prevention and that AHS guidance notes that giving prevention to heartworm-infected dogs may cause serious complications. This article uses the more measured language recommended in the fact-check review rather than absolute statements. The isoxazoline class warning is accurately described as an FDA class-wide communication. MDR1 concerns regarding moxidectin are addressed with appropriate nuance, noting that the dose in Simparica Trio is below toxic thresholds while still recommending veterinary consultation.