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Trifexis® is a chewable prescription medication used in dogs 8 weeks of age or older and at least 5 pounds to prevent and treat flea infestations, adult hookworm, adult roundworm, and adult whipworm infections. It is also used to prevent heartworm disease.
Trifexis® has two active ingredients, spinosad and milbemycin oxime. Spinosad works by causing an overload of nicotinic acetylcholine receptors in the insect’s nervous system. Spinosad is highly selective for insect receptors. It begins to kill fleas in about 30 minutes and kills up to 100% of fleas on dogs within 4 hours.
Milbemycin shifts chloride, a naturally occurring electrolyte, across the cell membrane of certain susceptible worms such as heartworms, roundworms, and hookworms. By overloading chloride into these worms, it affects the electrical activity within their nervous system, causing muscle paralysis and death. Mammals do not contain the same chloride movement channels as insects, which makes milbemycin an important ingredient in Trifexis®.
Trifexis® is a chewable tablet and is administered once a month with food. For heartworm prevention, the medication should be given once monthly for at least three months after exposure to mosquitoes. Follow the directions on the drug label or as provided by your veterinarian. If your dog vomits within an hour of administration, another full dose is recommended.
Speak with your veterinarian about what to do if you forget to give a dose of Trifexis®. Generally, they will advise you to administer a dose with food as soon as you remember, and then continue a monthly schedule from that date. In most cases, do not give extra or double doses.
As a pet parent, I’m always concerned about giving my furry friend medications, even when they’re necessary. Trifexis is a popular monthly chewable tablet that prevents heartworms, kills fleas, and treats hookworms, roundworms, and whipworms in dogs. But like any medication, it can sometimes cause unwanted side effects that might leave you wondering: can Trifexis make my dog sick?
The short answer is yes, Trifexis can sometimes make dogs sick but most reactions are mild and temporary. Let’s dive deeper into what you need to know if your dog experiences side effects from this common parasite preventative.
What is Trifexis and How Does It Work?
Before we talk about side effects, it’s important to understand what Trifexis actually is. This medication contains two active ingredients:
- Spinosad – Originally developed as a crop pesticide, it kills fleas
- Milbemycin oxime – An antiparasitic that prevents heartworms and treats intestinal parasites
Together, these ingredients provide broad-spectrum protection against multiple parasites in a single monthly dose. That’s why so many vets recommend it despite potential side effects – the protection it offers is crucial for your dog’s health.
Common Side Effects of Trifexis
Many dogs tolerate Trifexis well, but some do experience side effects. According to studies and information from the manufacturer, here are the most common side effects:
Short-Term Side Effects
| Side Effect | Frequency | Severity |
|---|---|---|
| Vomiting | Most common (6% of dogs) | Usually mild |
| Lethargy | Common (2.6% of dogs) | Mild to moderate |
| Diarrhea | Less common (2% of dogs) | Usually mild |
| Itching/Pruritus | Less common (4% of dogs) | Usually mild |
| Decreased appetite | Rare (1.2% of dogs) | Usually mild |
| Dermatitis | Rare (1.4% of dogs) | Usually mild |
These side effects typically resolve within 24-48 hours after giving the medication.
Long-Term or More Serious Side Effects
While rare, some dogs may experience more concerning side effects with long-term use:
- Neurological issues: Seizures, tremors, or loss of coordination
- Liver strain: Can lead to elevated liver enzymes
- Behavioral changes: Anxiety, aggression, or restlessness in some dogs
- Unexpected weight loss: May indicate organ stress
What to Do If Your Dog Vomits After Taking Trifexis
One of the most common concerns I hear from fellow dog owners is about vomiting after giving Trifexis. Here’s what to do if this happens:
If Your Dog Vomits Within 1 Hour of Taking Trifexis
- Contact your veterinarian immediately – They may recommend giving another dose
- Call Elanco’s customer service (the company that makes Trifexis)
- Contact Pet Poison Helpline if you’re concerned about toxicity
If Your Dog Vomits Several Hours Later or at Night
This could be more concerning, especially if accompanied by other symptoms. Contact an emergency vet clinic for advice.
Pro Tip: Always give Trifexis with food, about 10-15 minutes after your dog has eaten a full meal. This significantly reduces the chance of vomiting.
Is Trifexis Safe for All Dogs?
While Trifexis is FDA-approved and considered safe for most dogs, there are some situations where caution is needed:
Dogs That May Be More Sensitive to Trifexis
- Senior dogs – Older dogs may have declining liver or kidney function
- Dogs with pre-existing liver issues
- Dogs with a history of seizures or neurological problems
- Dogs with gastrointestinal sensitivity
- Dogs with autoimmune disorders
Before Starting Trifexis
Important: Your dog MUST be tested for heartworms before starting Trifexis. This medication is for prevention only – if your dog already has heartworms, Trifexis can cause serious reactions by killing microfilaria (baby heartworms) in the bloodstream.
The Trifexis Controversy: Is There Cause for Concern?
I’ve heard some scary stories online about Trifexis. There have been reports linking Trifexis to serious adverse effects including deaths in some dogs. However, it’s important to note that the FDA and Elanco (the manufacturer) have investigated these claims and found no direct connection between Trifexis and these tragic events.
Over 70 million doses of Trifexis have been administered since its launch in 2011. While there have been around 900 reports of deaths that owners linked to the medication, no scientific evidence has established a causal relationship.
Still, I always tell my friends to monitor their dogs closely after giving any medication, including Trifexis. Trust your instincts – you know your dog best!
How to Reduce the Risk of Side Effects
If you’re concerned about side effects but still want to use Trifexis, here are some strategies to minimize risks:
- Always give with food – This helps reduce gastrointestinal upset
- Monitor your dog after each dose – Watch for any unusual behavior or symptoms
- Consider regular blood tests – Especially for dogs on long-term treatment, to check liver function
- Keep a symptom diary – Note any changes after each dose to identify patterns
- Discuss alternatives with your vet if your dog consistently has reactions
Alternatives to Trifexis
If your dog doesn’t tolerate Trifexis well, don’t worry! There are other options for parasite prevention:
- Heartgard – Heartworm prevention only
- Sentinel – Similar combination product
- Nexgard – Primarily for fleas and ticks
- Bravecto – Longer-lasting flea and tick prevention
- Topical preventatives – May be gentler on sensitive dogs
When to Contact Your Vet Immediately
While mild side effects are common, some symptoms warrant immediate veterinary attention:
- Seizures or tremors
- Severe vomiting or diarrhea lasting more than 24 hours
- Extreme lethargy or collapse
- Yellowing of the eyes or gums (jaundice)
- Unexpected aggression or severe anxiety
- Difficulty breathing
The Bottom Line: Weighing Benefits and Risks
So, can Trifexis make your dog sick? Yes, it can cause side effects in some dogs, but for most, these effects are mild and temporary. The protection it provides against potentially deadly parasites like heartworms often outweighs the risks of side effects.
As a responsible pet parent, the best approach is to:
- Discuss your dog’s specific health profile with your vet
- Monitor your dog after giving Trifexis
- Report any concerning side effects to your vet and the manufacturer
- Consider alternatives if your dog consistently reacts poorly
Remember, heartworm disease is far more dangerous than the potential side effects of prevention medication. Working closely with your vet to find the right preventative strategy for your specific dog is the best way to keep them healthy and happy.
Have you noticed any side effects when giving your dog Trifexis? Share your experience in the comments below!
Disclaimer: I’m not a veterinarian, and this article isn’t meant to replace professional veterinary advice. Always consult with your vet about any medication concerns for your dog.
Trifexis® Possible Side Effects
Vomiting is the most common side effect seen with Trifexis®. This side effect can be lessened when Trifexis® is given on a full stomach, which also helps the body to absorb the medication.
Other side effects include:
- Fatigue (lethargy)
- Lack of appetite
- Itching
- Diarrhea
- Red ears or skin
- Drooling
- Trembling
- Loss of coordination
- Seizures
If you believe your animal may be experiencing any side effects, consult your veterinarian.
Human Side Effects
This medication is not used in humans. If you accidentally ingest a pet medication, call your physician or the national Poison Control Center hotline at 800-222-1222.
Prior to administration of Trifexis®, your dog should be tested for existing heartworm infection. While no specific monitoring is required for this medication, your veterinarian may recommend routine testing depending on your dog’s individual needs, other medications they may be on, or the issue that initially caused your pet to be placed on this medication.
Call Your Vet If:
- Severe side effects are seen (see above)
- Your dog’s condition worsens or does not improve with treatment
- You see or suspect an overdose
- You have additional questions or concerns about the use of Trifexis®
Symptoms of an overdose of Trifexis® are very similar to the listed side effects above, with vomiting as the most common sign of an overdose. Additional symptoms may include drooling, tremors, fatigue (lethargy), and coughing. If you suspect an overdose, immediately contact your veterinarian, seek emergency veterinary care, or contact an animal poison control center. Consultation fees often apply.
Trifexis® should be stored at controlled room temperatures between 68-77 F, and brief exposure to temperatures 59-86 F is acceptable. Always confirm storage requirements by reviewing the label.
Keep the medication in the provided blister packs until ready for use, to protect the chews from moisture and light.
Keep out of reach of children and pets.
Is Nexgard® the same as Trifexis®?
No. Trifexis® contains the active ingredients spinosad and milbemycin oxime. It is labeled to treat and prevent flea infestations, adult hookworm, adult roundworm, and adult whipworm infections. Trifexis® can also be used to prevent heartworm infections. Nexgard® contains the active ingredient afoxolaner, and is labeled to treat and prevent flea infestations and certain tick species.
No vet writer or qualified reviewer has received any compensation from the manufacturer of the medication as part of creating this article. All content contained in this article is sourced from public sources or the manufacturer.
Featured : Capuski
Dr. Stephanie Howe graduated from the University of Florida College of Veterinary Medicine in 2011, after receiving a Bachelor of Science…
Is Trifexis Safe for Dogs?
FAQ
What are the side effects of Trifexis for dogs?
The most common side effects include vomiting, diarrhea, and a loss of appetite, particularly in dogs that already have sensitive stomachs or conditions like IBD (inflammatory bowel disease). Trifexis contains spinosad, which targets fleas but can also irritate the gastrointestinal tract, leading to nausea or vomiting in sensitive dogs.
Can a dog eat a lot after taking Trifexis?
Some dogs also experience a temporary loss of appetite and may not eat their food at their usual meal times. Serious side effects are rare, but you should still monitor your dog after administering Trifexis and report any side effects that last a long time or get worse.
Is Trifexis safe for older dogs?
In addition, senior dogs are more prone to neurological side effects, such as tremors or seizures, which are rare but serious risks with Trifexis. These side effects can be more pronounced in older dogs, particularly those with pre-existing neurological conditions.
Does Trifexis have side effects?
Reducing the risk of side effects from long-term Trifexis use involves proactive monitoring and tailoring the treatment to your dog’s specific needs. Here are several strategies to minimize the potential for negative reactions: Administer with Food: Trifexis is known to cause gastrointestinal upset, particularly vomiting.
Will Trifexis affect my dog’s appetite?
Weight loss and appetite changes are potential, though less common, side effects of Trifexis. Some dogs may experience a temporary decrease in appetite following the administration of the medication, particularly if they feel nauseated or experience vomiting.
Can Trifexis cause tremors in dogs?
Neurological effects are one of the rare but serious risks associated with long-term Trifexis use. In some cases, dogs have developed tremors, ataxia (loss of muscle coordination), and even seizures after extended exposure to the medication.
What are the symptoms of Trifexis poisoning in dogs?
Symptoms of an overdose of Trifexis® are very similar to the listed side effects above, with vomiting as the most common sign of an overdose. Additional symptoms may include drooling, tremors, fatigue (lethargy), and coughing.
Why is my dog acting weird after taking trifexis?
Panting and restlessness might occur in some dogs after taking Trifexis and could be due to mild discomfort or a temporary reaction.
How bad is trifexis for dogs?
If spinosad kills fleas, is it safe for my dog? Trifexis has been demonstrated to be safe in healthy dogs when used according to label directions.
Can trifexis cause an upset stomach?
We have been prescribing Trifexis since it has been on the market and have found it be very safe and effective. The only side effects we have noted are vomiting, occasional diarrhea and, in rare cases, itching. Any medication taken orally can cause vomiting.