The label says, word for word:
SIMPARICA TRIO is indicated for the prevention of heartworm disease caused by Dirofilaria immitis and for the treatment and control of roundworm (immature adult and adult Toxocara canis and adult Toxascaris leonina) and hookworm (L4, immature adult, and adult Ancylostoma caninum and adult Uncinaria stenocephala) infections.
There are no known contraindications for the use of SIMPARICA TRIO.
Sarolaner, one of the ingredients in SIMPARICA TRIO, is a member of the isoxazoline class. This class has been associated with neurologic adverse reactions including tremors, ataxia, and seizures.
Seizures have been reported in dogs receiving isoxazoline class drugs, even in dogs without a history of seizures. Use with caution in dogs with a history of seizures or neurologic disorders.
Prior to administration of SIMPARICA TRIO, dogs should be tested for existing heartworm infections.
The safe use of SIMPARICA TRIO has not been evaluated in breeding, pregnant, or lactating dogs.
Not for use in humans. Keep this and all drugs out of reach of children. Keep SIMPARICA TRIO in a secure location out of reach of dogs, cats and other animals to prevent accidental ingestion or overdose.
Every approved medicine has a field study behind it, and the label prints what happened:
In a field safety and effectiveness study, SIMPARICA TRIO was administered to dogs for the prevention of heartworm disease.
The most frequent reactions reported in the SIMPARICA TRIO group are presented in the following table.
Table 1 (SIMPARICA TRIO group): Vomiting 14.3%; Diarrhea 13.2%; Lethargy 8.5%; Anorexia 5.1%; Polyuria 3.7%; Hyperactivity 2.2%; Polydipsia 2.2%
Approved by FDA under NADA 141-521; FDA announced the approval on March 2, 2020 (https://www.fda.gov/animal-veterinary/cvm-updates/fda-approves-simparica-trio-combination-drug-heartworm-and-other-parasites). The label's full indication also covers fleas, six tick species and Lyme prevention for 'dogs and puppies 8 weeks of age and older, and weighing 2.8 pounds or greater'; the label states verbatim: 'SIMPARICA TRIO is indicated for the prevention of Borrelia burgdorferi infections as a direct result of killing Ixodes scapularis vector ticks.'
The emergency page sorts the signs by how long you have, and the symptom checker asks what you are seeing. Reactions to a medicine can also be reported to the FDA yourself: how to report a problem.
These answers come from the approved label on DailyMed, read on 2 October 2026. Where the label does not say, the answer says so, and the vet or the pharmacist is the one to ask.
The approved use is quoted at the top of this page. It is a chewable tablet given once a month to dogs and puppies 8 weeks of age and older that weigh 2.8 pounds or more. It prevents heartworm disease, kills fleas, treats and controls the ticks the label names, and treats roundworms and hookworms.
The label says that in a laboratory study Simparica Trio began to kill fleas at 4 hours and was 100% effective at 8 hours after the first dose. In another laboratory study it began to kill black-legged ticks already on the dog within 8 hours. For the other ticks on the label, the results are given at 48 or 72 hours after the dose.
It is given by mouth once a month, with or without food. Make sure your dog eats the complete dose and that no part of it is lost or refused. For heartworm prevention the label says to give it every month all year round, or at least from within one month of the dog's first seasonal exposure to mosquitoes until at least one month after the last. The label says dogs should be tested for heartworm infection before the first dose. When it replaces another monthly heartworm preventive, the label says to give it within one month of the last dose of that product. The label does not say what to do if your dog vomits soon after a dose, so call the clinic if that happens.
The label says: "If a dose is missed, give SIMPARICA TRIO immediately and resume monthly dosing." In plain words, give the tablet and carry on once a month.
The studies and the warnings are quoted above. The label has no line telling owners when to call the vet. It does say that one of its ingredients belongs to a drug class that has been linked to tremors, unsteady walking and seizures, and that seizures have been reported even in dogs with no history of them. If you see any of these, or your dog seems unwell after a dose, call the vet.
Store it at or below 86°F. Keep it out of the reach of children. The label also says to keep it in a secure place out of reach of dogs, cats and other animals, to prevent accidental swallowing or an overdose.
The FDA says the best way to get rid of most unused or expired medicines is a take-back option: a drug take-back location, which can be at a pharmacy or a police station, or a prepaid mail-back envelope. If you cannot use one and the medicine is not on the FDA's flush list, the FDA says to mix it, uncrushed, with something unappealing such as dirt, cat litter or used coffee grounds and to seal the mixture in a plastic bag before throwing it away. Flushing is only for medicines on that list, such as opioids. Do not give leftovers to another pet.
Write the dose, the times and the stop date here, then print this page for the fridge.
Dose and times: _____________________________________________
Stop date: _____________________________________________