Interceptor and Interceptor Plus for Dogs: Uses and Side Effects

What Is Interceptor Used for in Dogs?

Interceptor is a prescription medication for dogs that is used to help prevent heartworm disease and treat common intestinal parasites—roundworms, hookworms, and whipworms. It's FDA-approved for use in dogs and comes as a flavored chewable tablet. 

How Does Interceptor Work in Dogs?

Interceptor contains milbemycin oxime, which works by interfering with the nerve transmission of parasites, causing paralysis and death. This helps kill immature heartworm larvae and eliminate intestinal worms. 

What Is Interceptor Plus for Dogs?

Interceptor Plus is a combination prescription medication for dogs that is used to help prevent heartworm disease and treat additional intestinal parasites, including tapeworms. It's FDA-approved for use in dogs and comes as a flavored chewable tablet. 

How Does Interceptor Plus Work in Dogs?

Interceptor Plus combines two active ingredients:  

• Milbemycin oxime, which disrupts nerve function in parasites 
• Praziquantel, which damages tapeworms 

Together, these ingredients help kill immature heartworm larvae, eliminate intestinal worms, and treat tapeworm infections. 

Interceptor and Interceptor Plus Considerations for Dogs

Some dogs may need extra precautions when taking Interceptor or Interceptor Plus. Before starting these medications, keep the following considerations in mind: 

• Dogs should be tested for heartworm disease before starting this medication. 
• Use with caution in dogs who are already heartworm-positive. 
• Use only in puppies and dogs who are 4 weeks of age or older (Interceptor) or 6 weeks of age or older (Interceptor Plus), weighing at least 2 pounds. 
• The safety of Interceptor Plus has not been tested in dogs used for breeding or in lactating females, but Interceptor is considered safe for breeding, pregnant, and lactating females. 
• Tell your veterinarian about any other medications or supplements your dog is taking 

What Is the Difference Between Interceptor and Interceptor Plus?

Interceptor Plus contains praziquantel in addition to milbemycin oxime, allowing it to treat tapeworms, while Interceptor does not. 

How Do You Give Interceptor and Interceptor Plus to Dogs?

Follow the directions on the drug label or as provided by your veterinarian. Interceptor and Interceptor Plus are given in similar ways but always confirm specific instructions on your product label. 

• Give once monthly. 
• Administer orally (chewable tablet). 
• Interceptor can be given with or without food. Interceptor Plus is often given with food, but follow your veterinarian’s guidance. 
• Ensure the full dose is consumed. If you think some of it didn’t stay down or was spit out, give another full dose as soon as you can. 
• Give year-round for best protection. 

What Happens If You Miss a Dose of Interceptor or Interceptor Plus? 

Speak with your veterinarian about what to do if a dose is missed. Generally, your vet may instruct you to give it when you remember, or if it's almost time for your dog's next dose, to skip the missed dose and resume your normal dosing schedule. Do not give extra or double doses. 

What Are the Side Effects of Interceptor and Interceptor Plus in Dogs?

Interceptor and Interceptor Plus are generally well-tolerated, but side effects can occur.  

Both medications share many of the same side effects because they contain milbemycin oxime. Interceptor Plus also contains praziquantel, which may increase the likelihood of mild gastrointestinal signs in some dogs.  

Possible side effects may include: 

• Vomiting 
• Diarrhea 
• Lethargy 
• Drooling 
• Loss of appetite 
• Ataxia (loss of coordination) 
• Tremors (rare) 
• Seizures (very rare) 

Serious neurologic side effects are uncommon but may occur, especially in dogs with sensitivities to this class of medication. 

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 contact Poison Control at 800-222-1222. 

Monitoring Your Pet 

No specific ongoing monitoring is typically required for this medication; however, dogs should be tested for heartworm disease before starting Interceptor or Interceptor Plus, and your veterinarian may recommend periodic or annual heartworm testing based on your pet’s individual needs. 

When Should You Call Your Veterinarian? 

Call your veterinarian if you notice any of the following, or if you have additional questions or concerns about the use of Interceptor or Interceptor Plus: 

• Severe side effects occur (such as persistent vomiting or diarrhea) 
• Your dog's condition worsens or does not improve 
• You suspect an overdose 

What Happens If a Dog Overdoses on Interceptor or Interceptor Plus?

An overdose of Interceptor or Interceptor Plus may cause neurologic symptoms such as tremors, weakness, or seizures. Because Interceptor Plus also contains praziquantel, some dogs may additionally experience gastrointestinal signs. 

• Tremors 
• Seizures 
• Loss of coordination 
• Excessive salivation 

If you suspect an overdose, seek emergency veterinary care or contact an animal poison control center, such as: 

• Pet Poison Helpline (855-764-7661) 
• ASPCA Animal Poison Control Center (888-426-4435) 

How Should Interceptor and Interceptor Plus Be Stored?

Keep the following storage tips in mind for these medications: 

• Store at controlled room temperature, typically between 59–77 F (15–25 C). 
• Protect from moisture and light. 
• Keep in the original packaging until use. 
• Keep out of reach of pets and children.