Interceptor® (Milbemycin Oxime) for Dogs and Cats: Uses, Dosage, and Side Effects

Interceptor® is a monthly prescription medication that helps prevent heartworm disease and treat certain intestinal parasites in dogs and cats. Interceptor® Plus contains an additional ingredient that also protects dogs against tapeworms.

Here’s how Interceptor®, Interceptor® Plus, dosing, side effects, and safety recommendations compare.

What is Interceptor®?

Interceptor® is a monthly prescription medication that contains milbemycin oxime and is used to prevent heartworm disease in dogs and cats. It also treats and controls certain intestinal parasites.

For dogs:

• Prevents heartworm disease
• Controls hookworms
• Treats and controls roundworms and whipworms
• Approved for dogs and puppies 4 weeks of age and older that weigh more than 2 pounds

For cats:

• Prevents heartworm disease
• Treats roundworms and hookworms
• Approved for cats and kittens 6 weeks of age and older that weigh more than 1.5 pounds

What Is Interceptor® Plus?

Interceptor® Plus is a monthly prescription medication for dogs that contains milbemycin oxime and praziquantel. It helps prevent heartworm disease while treating and controlling several intestinal parasites, including tapeworms.

Interceptor® Plus:

• Prevents heartworm disease
• Treats and controls hookworms
• Treats and controls roundworms
• Treats and controls whipworms
• Treats and controls tapeworms

Interceptor® Plus is approved for dogs and puppies 6 weeks of age and older that weigh more than 2 pounds.

How Interceptor® and Interceptor® Plus Work

Interceptor® and Interceptor® Plus work by paralyzing and killing certain parasites. Both medications contain milbemycin oxime, while Interceptor® Plus also contains praziquantel, which provides additional protection against tapeworms.

Milbemycin oxime: The primary active ingredient in both Interceptor® and Interceptor® Plus, milbemycin oxime shifts chloride—a naturally occurring electrolyte—across the cell membranes of susceptible parasites, including heartworms, roundworms, hookworms, and whipworms.

This disrupts the parasites' nervous system, causing muscle paralysis and death.

Praziquantel: Interceptor® Plus contains a second active ingredient, praziquantel, which provides protection against tapeworms. Although its exact mechanism isn't fully understood, praziquantel is believed to disrupt the worms' muscle integrity, resulting in paralysis.

How To Give Interceptor® and Interceptor® Plus

Interceptor® and Interceptor® Plus are given by mouth once a month to help prevent heartworm disease and treat certain intestinal parasites.

When giving Interceptor® or Interceptor® Plus:

• The medication may be given with or without food.
• The chewable tablet may be broken into smaller pieces if needed to make administration easier.
• For Interceptor® Plus, try to ensure your dog chews the tablet instead of swallowing it whole.
• If your dog or cat does not consume the entire chewable tablet, give a new chewable to ensure they receive the full dose.

Missed a Dose?

If you miss a dose of Interceptor® or Interceptor® Plus, give it as soon as you remember.

Continue giving the medication as close to every 30 days as possible. If your veterinarian has prescribed a different dosing schedule, contact them for instructions if a dose is missed.

Do not give extra or double doses.

Interceptor® and Interceptor® Plus Side Effects

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

Possible side effects include:

• Vomiting
• Diarrhea
• Loss of appetite
• Lethargy
• Lack of coordination
• Drooling or excessive salivation
• Weakness
• Convulsions

Human Side Effects

Interceptor® and Interceptor® Plus are not intended for use in humans.

If you accidentally ingest this medication, contact your physician or the National Poison Control Center immediately at 800-222-1222.

Monitoring

Pets should be tested for heartworm infection before starting Interceptor® or Interceptor® Plus.

Your veterinarian may recommend additional monitoring based on your pet's health and medical history.

Important monitoring considerations include:

• Dogs with existing heartworm infections should first be treated to eliminate adult heartworms before restarting Interceptor® or Interceptor® Plus.
• Interceptor® and Interceptor® Plus kill heartworm microfilariae, which can trigger an allergic reaction in heartworm-positive dogs.
• The safety of Interceptor® in heartworm-positive cats has not been established.
• Additional monitoring or routine testing may be recommended depending on your pet's individual needs.

When To Call Your Veterinarian

Contact your veterinarian if:

• Your pet develops severe side effects.
• Your pet's condition worsens or does not improve with treatment.
• You suspect your pet has received an overdose.
• You have additional questions or concerns about using Interceptor® or Interceptor® Plus.

Interceptor® and Interceptor® Plus Overdose

An overdose of Interceptor® or Interceptor® Plus can cause serious side effects and requires immediate veterinary attention.

Common signs of an overdose include:

• Vomiting
• Incoordination
• Lethargy
• Drooling
• Tremors

If you suspect your pet has received an overdose, contact your veterinarian immediately, seek emergency veterinary care, or call an animal poison control center. Consultation fees may apply.

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

How To Store Interceptor® and Interceptor® Plus

Store Interceptor® and Interceptor® Plus at room temperature in their original packaging to help protect the medication from heat, moisture, and light.

Storage instructions:

• Store at controlled room temperatures between 59 F and 77 F (15 C–25 C).
• Keep the medication in its original blister pack until you are ready to administer it to protect it from moisture and light.
• Keep out of reach of children and pets.