What to Do If Your Dog Vomits After Taking Trifexis

Administering the heartworm and flea preventative, Trifexis, to your beloved pooch should be an uneventful task. However, sometimes, our canine companions may vomit shortly after ingesting the pill. The key question dog owners often find themselves asking is – should I redose or not?

Why Do Dogs Vomit After Taking Trifexis?

Trifexis, a combination of Spinosad and Milbemycin, can be potent on an empty stomach, leading to common side effects such as vomiting. Though it doesn’t typically indicate toxicity or severe problems, it can be an unpleasant experience for your dog. It’s always essential to administer Trifexis after a full meal to help mitigate this issue.

Should You Redose After Your Dog Vomits?

The key factor determining whether to redose or not is the timing of the vomit. According to the manufacturer’s guidelines, you should only consider a redose if the dog vomits within an hour of administering Trifexis. This is because the medicine needs a specific time frame to be adequately absorbed into the dog’s system. If the vomit occurs within this window, there’s a chance that the pill might not have been fully absorbed.

What If Vomiting Occurs After the One-Hour Window?

If your dog vomits after the one-hour mark, there’s a high probability that enough of the medication was absorbed to provide its protective benefits. In this case, you shouldn’t redose. If you’re uncertain, it’s always best to consult with your veterinarian.

Steps to Minimize Vomiting After Trifexis

While there’s no foolproof method to prevent vomiting, these steps can decrease the chances:

  1. Administer Trifexis With Food: Giving your dog Trifexis after a full meal can significantly decrease the chances of vomiting.
  2. Divide the Dosage: Breaking the dose into two and administering half before the meal and half after could be beneficial.
  3. Observe Your Dog: Keep a close eye on your pet for an hour post-medication to monitor any signs of discomfort or sickness.

When to Consult Your Veterinarian

While occasional vomiting after taking Trifexis can be normal, continuous or severe reactions necessitate an immediate vet consultation. If your dog vomits every time you administer Trifexis, your vet might need to consider an alternative medication or investigate an underlying issue.


Vomiting after administering Trifexis can be a worrisome event for dog owners. Understanding the causes, when to redose, and how to prevent such occurrences can help maintain your pet’s comfort and health. Remember, if ever in doubt, always consult with your vet to ensure your furry friend receives the best care possible.


Q1: Is Trifexis safe for all breeds of dogs?

Trifexis is generally considered safe for use in most breeds of dogs. However, some breeds, especially collies and other herding breeds, may be sensitive to Milbemycin, one of the ingredients in Trifexis. These dogs may require a lower dose or alternative medication. Always consult with your vet before starting any new medication regimen for your pet.

Q2: Can my puppy take Trifexis?

Trifexis is approved for use in dogs and puppies 8 weeks of age or older and weighing at least 5 pounds. However, it’s important to talk with your vet to determine if it’s the right choice for your young dog.

Q3: What are the common side effects of Trifexis?

Common side effects may include decreased appetite, lethargy, and diarrhea, in addition to vomiting. Although these side effects are usually mild and transient, consult with your vet if they persist or if you observe any unusual behaviors in your pet.

Q4: How quickly does Trifexis start working?

Trifexis starts killing fleas within 30 minutes of administration and eliminates 100% of biting fleas within four hours. It also starts preventing heartworm disease immediately after it’s administered.

Q5: Can I give my dog Trifexis with other medications?

Trifexis can be given along with some other medications, but not all. It’s important to inform your vet about all the medications and supplements your dog is currently taking. Some drug interactions could potentially be harmful.

Q6: What should I do if my dog repeatedly refuses to take Trifexis?

If your dog consistently resists taking Trifexis, you can try disguising the pill in a tasty treat. If this doesn’t work, consult with your vet for alternative solutions, which might include using different medications with similar effects.

Q7: What are the symptoms of a Trifexis overdose?

In case your dog ingests more than the recommended dosage of Trifexis, symptoms might include vomiting, salivation, tremors, and decreased activity. If you suspect an overdose, contact your vet or an emergency veterinary clinic immediately.

Q8: What happens if I miss a dose of Trifexis?

If you miss a dose, administer Trifexis immediately when you remember and resume your monthly schedule. Never give two doses at once. Consistency is key in ensuring effective heartworm and flea prevention.

Q9: Can Trifexis be used in pregnant or lactating dogs?

The safety of Trifexis in breeding, pregnant, or lactating dogs has not been evaluated. If your dog is pregnant or nursing, please consult your vet before administering Trifexis.

Q10: Can Trifexis cause long-term health issues in dogs?

There are no known long-term adverse effects of Trifexis when used as directed. However, each dog is unique, and it’s always advisable to discuss your pet’s health history and any concerns with your vet.

Q11: Why should Trifexis be given with a meal?

Trifexis should be given with food, or immediately after a meal, as this helps to ensure full absorption of the drug and minimizes the risk of your dog vomiting after administration.

Q12: Are there any natural alternatives to Trifexis?

There are natural flea and tick remedies available, such as diatomaceous earth, certain essential oils, and dietary supplements. However, these natural options might not provide comprehensive protection against heartworms, fleas, and intestinal parasites like Trifexis does. Always consult with your vet before changing your pet’s parasite prevention regimen.

Q13: Can I use Trifexis for my cat?

Trifexis is not approved for use in cats. It’s specifically designed and tested for dogs, and the safety and efficacy for other species have not been established. Always use a species-appropriate medication for your pets.

Q14: What happens if my dog vomits a long time after taking Trifexis?

If your dog vomits several hours after taking Trifexis, it’s likely that the medication has already been absorbed. However, if you’re uncertain, it’s best to contact your vet for advice.

Q15: Can I switch from another heartworm/flea medication to Trifexis?

Yes, you can switch from another heartworm or flea medication to Trifexis. It’s important, however, to consult with your vet to ensure a smooth transition and to avoid any gaps in protection.

Q16: Does Trifexis protect against ticks?

While Trifexis is highly effective against fleas, heartworms, and several kinds of intestinal parasites, it does not provide protection against ticks. If ticks are a concern in your area, discuss with your vet about additional tick prevention strategies or alternative products that also cover tick protection.

Q17: Can humans be harmed by handling Trifexis?

There’s no known risk to humans from handling Trifexis. However, as with any medication, wash your hands after administering the drug to your pet.

Q18: Is weight an important factor when dosing Trifexis?

Yes, Trifexis dosages are based on the weight of your dog. It’s crucial to give the correct dosage to ensure effectiveness and prevent potential side effects. Regularly check your dog’s weight and adjust the dosage as necessary under your vet’s guidance.

Q19: My dog has a history of seizures. Can he still take Trifexis?

In some rare cases, Trifexis has been associated with seizures in dogs. If your dog has a history of seizures, consult with your vet before starting Trifexis. Your vet may recommend a different product or closely monitor your pet while on Trifexis.

Q20: Can my dog develop immunity to Trifexis?

There is currently no evidence that dogs can develop immunity to Trifexis. It should continue to be effective as long as it’s administered properly and consistently, according to your vet’s recommendations.

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