Simparica and Simparica Trio for Dogs: Uses and Side Effects

PetMD’s medications content is written and reviewed by veterinary professionals to answer common questions about how medications work, their side effects, and what species they are prescribed for. This content should not replace advice from your veterinarian. 

What Is Simparica Used for in Dogs?

Simparica (sarolaner) is a ​monthly oral flea and tick preventive for dogs​. 

It’s FDA-approved to treat and prevent flea infestations and to treat and control Gulf Coast ticks, American dog ticks, black-legged ticks, Lone Star ticks, brown dog ticks​, ​​and Asian longhorn ticks​ in dogs 6 months of age and older who weigh at least 2.8 pounds. 

Simparica ​may ​also ​be ​prescribed ​by veterinarians ​​for​ extra-label ​use ​to treat demodectic mange, sarcoptic mange, and ear mites​ in dogs​. These uses are not listed on the FDA-approved label. ​A v​eterinarian will determine whether ​extra-label ​use is ​appropriate ​for your dog.  

What Is Simparica Trio Used for in Dogs?

Simparica Trio (sarolaner, moxidectin, and pyrantel) is a ​monthly oral flea, tick, and heartworm preventive for dogs​. 

It’s FDA-approved to treat and prevent flea infestations, treat and control multiple tick species, prevent heartworm disease caused by Dirofilaria immitis, and treat and control roundworms and hookworms in dogs 8 weeks of age and older who weigh at least 2.8 pounds.

Simparica Trio combines three active ingredients: sarolaner (flea and tick control), moxidectin (heartworm prevention), and pyrantel (intestinal parasite treatment). 

Simparica and Simparica Trio Considerations for Dogs

Use caution or speak with your veterinarian before giving Simparica or Simparica Trio to dogs who:

• Have a history of seizures or neurologic disorders 

• Are younger than the labeled age or below the minimum weight requirement  

• Have tested positive for heartworm disease 

• Are pregnant, breeding, or lactating 

Always discuss with your veterinarian your dog’s full medical history and any other medications or supplements they are taking before starting a new preventive. 

How Do Simparica and Simparica Trio Work in Dogs?

Simparica kills fleas and ticks by overstimulating their nervous system, leading to paralysis and death. Simparica Trio also prevents heartworm disease and treats certain intestinal worms. 

Simparica contains: 

• Sarolaner (isoxazoline): Kills fleas and ticks by disrupting their nervous system​; ​​f​leas begin to die within hours after biting a treated dog 

Simparica Trio contains: 

• Sarolaner: Kills fleas and ticks​     ​ 

• Moxidectin: Prevents heartworm disease and treats roundworms and hookworms​     ​ 

• Pyrantel: Paralyzes intestinal worms so they can be passed in feces​     ​ 

How Do You Give Simparica and Simparica Trio to Dogs?

​​Follow the directions on the drug label for Simparica or Simparica Trio or as provided by your veterinarian.​ ​​​​These medications are given​ by mouth​ once monthly.   

• Give on the same day each month to maintain protection. 

• Offer the chewable tablet by hand or with a small amount of food​; it ​can be given with or without food. 

• ​​Ensure your dog consumes the full dose​​ and u​se the correct product size based on your dog’s current weight​ and age​. 

• If vomiting occurs shortly after dosing​,​ or if you​’​re unsure whether your dog received the full dose, contact your veterinarian for guidance. 

What Happens If You Miss a Dose of Simparica or Simparica Trio? 

​​If you miss a dose, contact ​your veterinarian ​for guidance.​  

Generally, your vet may ​recommend giving the dose as soon ​​as ​you remember and ​then continuing ​your normal ​monthly ​schedule. 

Do not give extra or double doses.  

If ​a significant amount of time has passed ​since the last dose, you​r dog may be​ temporarily unprotected against fleas. ​Your veterinarian may ​also ​recommend a heartworm test if you​’re ​using Simparica Trio. 

What Are the Side Effects of Simparica and Simparica Trio in Dogs?

​​Simparica and Simparica Trio are generally well tolerated, but side effects can occur.​ Common side effects may include: 

• Vomiting 

• Diarrhea 

• Lethargy 

• Loss of appetite 

​​Neurologic side effects have been reported with ​medications in this class (​isoxazoline​s)​. Use caution in dogs with a history of seizures.​ ​​​​Neurologic side effects may include: 

• Muscle tremors 

• Lack of coordination (ataxia) 

• Seizures 

Human Side Effects 

Humans should never take medication prescribed for pets, and pets should not be given medication prescribed for humans. Dosages often differ significantly. 

If you accidentally ingest a pet medication, seek medical attention or call Poison Control at ​800-222-1222​. 

Monitoring Your Pet 

Dogs should be tested for existing heartworm infection before starting Simparica Trio. 

• Simparica Trio prevents heartworm disease but does not treat adult heartworms. 

• Dogs who test positive require appropriate treatment to remove adult heartworms before using this medication. 

Your veterinarian may recommend additional monitoring or routine testing based on your dog’s health history and individual risk factors. 

When Should You Call Your Veterinarian? 

​​Call your veterinarian if you see any of the following or if you have additional questions or concerns about the use of Simparica or Simparica Trio:​​​​​  ​​ 

• Severe side effects occur  

• Your pet’s condition worsens or does not improve  

• You suspect an overdose 

What Happens If a Pet Overdoses on Simparica or Simparica Trio?

An overdose of Simparica or Simparica Trio may increase the risk of gastrointestinal or neurologic side effects. 

Signs of overdose may include: 

• Vomiting 

• Diarrhea 

• Lethargy 

• Hypersalivation (excess drooling) 

• Muscle tremors 

• Lack of coordination (ataxia) 

• Seizures 

If you suspect an overdose, seek emergency veterinary care or contact an animal poison control center. Consultation fees may apply. 

• ​​Pet Poison Helpline​: 855-764-7661 

• ​​ASPCA Animal Poison Control​: 888-426-4435 

How Should Simparica and Simparica Trio Be Stored?

Keep the following storage tips in mind for this medication: 

• Store Simparica and Simparica Trio at or below 86 F (30 C). Brief exposure up to 104 F (40 C) is acceptable. Always confirm storag​e instructions on the product label​. 

• Keep the medication in the original blister pack until ready to use to protect it from moisture and light. 

• ​​A​void excessive heat or humidity. 

• Do not use the medication past the expiration date listed on the package. 

• Keep out of reach of children and pets.