Interceptor for Dogs: This Medication Kicks Worms to the Curb
Key takeaways:
Interceptor and Interceptor Plus are common parasite preventives for dogs. When given monthly, Interceptor prevents heartworms, hookworms, roundworms, and whipworms.
Interceptor and Interceptor Plus are only available for dogs via prescription, and they come as tablets or chewable tablets for dogs.
The risk of side effects associated with Interceptor or Interceptor Plus is low. But dogs may experience vomiting, diarrhea, loss of appetite, or lethargy.
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Table of contents
Interceptor (milbemycin oxime) and Interceptor Plus (milbemycin oxime / praziquantel) are medications that treat parasites in dogs. They’re important monthly parasite preventives for many dogs.
Read on to learn more about Interceptor and Interceptor Plus, including dosage, side effects, and more.
Interceptor for dogs at a glance
Common names | Milbemycin oxime (Interceptor) and milbemycin oxime / praziquantel (Interceptor Plus) |
What it treats | Parasites, including heartworms, hookworms, roundworms, and whipworms |
How it comes (forms) | Tablets, chewable tablets |
Dosage | Based on your dog’s weight |
Common side effects | Vomiting, diarrhea, lethargy, lack of appetite, wobbly gait |
Average cost |
What are Interceptor and Interceptor Plus used for in dogs?
Interceptor (milbemycin oxime) and Interceptor Plus (milbemycin oxime / praziquantel) are commonly prescribed parasite preventives for dogs. They work by interfering with nerve transmission in parasites, causing them to die.
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Interceptor and Interceptor Plus are FDA-approved for dogs to protect against the following parasites:
Interceptor may also be used to treat other conditions off-label, including:
Demodectic mange (demodex)
Sarcoptic mange (scabies)
Interceptor vs. Interceptor Plus
Interceptor and Interceptor Plus are similar parasite preventives for dogs. They have the same main ingredient: milbemycin oxime. But Interceptor Plus also contains praziquantel. Praziquantel helps kill tapeworms, adding an additional protection against parasites for dogs.
What is the right Interceptor dosage for dogs, and how is it given?
In general, dogs need a minimum Interceptor dosage of 0.23 mg per pound of body weight. For dogs taking Interceptor Plus, they should also get a minimum of praziquantel.
Interceptor comes as a tablet, while Interceptor Plus comes as a chewable tablet. Give your dog Interceptor or Interceptor Plus once a month or as otherwise directed by your veterinarian. You can give them with or without food.
What worms do you see? Learn what worms you might see in your dog’s poop and what to do if you suspect your pup has a dreaded case of parasites.
Heartworm treatment costs: If your dog does get heartworm disease, it can be expensive to treat. See what to expect if your dog gets this diagnosis.
Heartworm prevention matters: You may wonder whether your dog really needs heartworm prevention. We’d say yes, and here’s why.
Interceptor and Interceptor Plus for dogs are available by prescription only. Your veterinarian will prescribe the correct dosage of Interceptor or Interceptor Plus for your dog. Look for the correct package based on your pup’s weight.
Interceptor dosages for dogs
The table below shows the packaging color and dosage of Interceptor for dogs based on their weight.
Dog’s weight | Package color | Dosage |
2-10 lbs | Brown | 2.3 mg |
11-25 lbs | Green | 5.75 mg |
26-50 lbs | Yellow | 11.5 mg |
51-100 lbs | White | 23 mg |
Dogs who weigh more than 100 pounds will be prescribed a combination of these Interceptor tablets so they get the right dosage.
Interceptor Plus dosages for dogs
Below are the dosages for the two active ingredients in Interceptor Plus based on a dog’s weight.
Dog’s weight | Milbemycin oxime dosage | Praziquantel dosage |
2-8 lbs | 2.3 mg | 22.8 mg |
8.1-25 lbs | 5.75 mg | 57 mg |
25.1-50 lbs | 11.5 mg | 114 mg |
50.1-100 lbs | 23 mg | 228 mg |
Dogs who are over 100 pounds will take a combination of Interceptor Plus tablets to ensure they get the correct dosage.
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What should you do if your dog misses a dose of Interceptor or Interceptor Plus?
If your dog misses a dose of Interceptor or Interceptor Plus, give them the missed dose as soon as you remember. Then, continue giving your dog the medication on the recommended dosing schedule.
If your dog misses multiple monthly doses of Interceptor or Interceptor Plus, they may be more likely to become infected with heartworms or intestinal parasites. Talk to your veterinarian about their missed doses to determine whether additional testing is needed.
What are the common side effects of Interceptor in dogs?
Interceptor and Interceptor Plus have a low risk of side effects in most dogs. Dogs who do have side effects while taking these medications may experience:
Nausea
Lack of energy
Wobbly gait
Weakness
Increased salivation
Dogs with the MDR1 mutation are more prone to side effects, because they do not metabolize medications normally. The MDR1 mutation is most common in collies and Australian shepherds. Dogs with this mutation usually do not have problems with Interceptor or Interceptor Plus given once monthly at the correct dose. But they may become ill with higher or more frequent doses.
What are the most serious risks of Interceptor for dogs?
The most serious risks of Interceptor occur if your dog has an active heartworm infection. Giving your pup Interceptor or Interceptor Plus can lead to a rapid die-off of heartworms within the body. This can cause a severe reaction.
Signs of a serious Interceptor shock reaction associated with heartworm disease may include:
Labored breathing
Lack of energy
Severe, acute vomiting
Increased salivation
Death
Your veterinarian will test your dog for heartworms before prescribing Interceptor. Dogs with heartworms require special treatment and should not start Interceptor without veterinary supervision.
Which dogs shouldn't take Interceptor or Interceptor Plus?
Dogs who weigh less than 2 pounds should not be given Interceptor or Interceptor Plus. Puppies who are less than 4 weeks olds should not take Interceptor. Puppies under 6 weeks old should not be given Interceptor Plus.
Does Interceptor interact with any other dog medications?
In most cases, Interceptor does not interact with other dog medications. Interceptor Plus, which contains praziquantel, can interact with the following medications:
Cimetidine
Other interactions may occur in dogs with the MDR1 mutation who take either Interceptor or Interceptor Plus. If your dog is a high-risk breed, genetic testing can determine whether they have this mutation.
Interceptor and Interceptor Plus should only be given with a veterinarian’s prescription. Your veterinarian will let you know if they could interact with other medications your dog takes.
Frequently asked questions
Heartgard Plus (ivermectin / pyrantel pamoate) is similar to Interceptor and Interceptor Plus. But Interceptor, and especially Interceptor Plus, are FDA-approved to prevent more types of worms than Heartgard.
Interceptor prevents heartworms, hookworms, roundworms, and whipworms. Interceptor Plus also prevents tapeworm. Heartgard Plus prevents only heartworms, hookworms, and roundworms.
No, Interceptor does not kill fleas on dogs. It is FDA-approved to treat only intestinal parasites, including heartworms, roundworms, hookworms, and whipworms.
The bottom line
Interceptor (milbemycin oxime) and Interceptor Plus (milbemycin oxime / praziquantel) are commonly prescribed parasite preventive medications for dogs. When given once a month, Interceptor offers effective prevention against heartworms, hookworms, roundworms, and whipworms. Interceptor Plus can also prevent tapeworms in dogs. Less commonly, Interceptor may be used to treat conditions caused by other parasites. The risk of side effects in dogs is low with these medications, as long as they are given under the direction of a veterinarian.
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References
Brooks, W. (2024). Praziquantel (Droncit). Veterinary Partner.
Brooks, W. (2025). Milbemycin oxime. Veterinary Partner.
College of Veterinary Medicine. (2021). Dog breeds commonly affected by MDR1 mutation. Washington State University
Cornell Richard P. Riney Canine Health Center. (n.d.). Drug sensitivity: MDR1. Cornell University College of Veterinary Medicine.
Elanco U.S. (2020). Interceptor Plus [package insert].
Elanco U.S. (2021). Interceptor [package insert].
Elanco U.S. (2024). Interceptor Plus- milbemycin oxime and praziquantel tablet, chewable [package insert]. DailyMed.
Humane World for Animals. (n.d.). Preventing and treating heartworms in dogs.
U.S. Food and Drug Administration. (n.d.). Interceptor Plus- milbemycin oxime and praziquantel tablet, chewable [package insert].
U.S. Food and Drug Administration. (2022). Keep the worms out of your pet’s heart! The facts about heartworm disease.
