Side Effects from Common Flea and Tick Products

Isoxazoline-based products used for the prevention and treatment of fleas, ticks, and mites (Bravecto, Bravecto Plus, Nexgard, Simparica, Simparica Trio, Credelio, Revolution Plus) are gaining popularity. Many traditional (and even some holistic) veterinarians strongly recommend the use of isoxazoline-class products. Unfortunately, as the number of animals being given these products has risen, so has the number of pet owners reporting neurological and other adverse reactions.

What side effects are possible when using these drugs?

Neurological side effects or adverse reactions can range from barely noticeable to severe. Adverse reactions to these compounds appear to affect animals randomly, although those with certain chronic diseases, the young and elderly, and animals that are immune-compromised or have the genetic mutation of the MDR1 gene seem to be at higher risk. A survey of pet owners showed that adverse reactions are common.

Some adverse reactions that my clients have seen include:

• Aggression

• Personality changes

• Seizures

• Disorientation

• Wobbling or unstable gait

• Sensitivity to touch

• Abnormal vocalizations

• Urinary or fecal incontinence

• Death

I have seen these adverse reactions occur immediately after administration, but I have also worked with cases where the pet parent noticed them days, weeks, or even months later. Sometimes the reactions don’t occur until multiple doses of the medication have been given.

Other side effects that have been reported include:

• Liver failure

• Kidney failure 

• Dry eye

• Clotting disorders

• Internal hemorrhage

• Skin disease and itching

• Vomiting

• Diarrhea

• Inappetence

• Drooling

  
  

What should I do if I believe my pet is having an adverse reaction?

First and foremost, take your pet to the veterinarian immediately if you believe your animal is having an adverse reaction.  Many pet owners like that some of these products come in tablet form, which makes administration easy. The problem with this form of administration (oral ingestion) for any medication is that once it is ingested by the animal, it cannot be easily removed unless the patient is presented within an hour of dosing. In my clinics, I did see some emergency cases where a pet would come in experiencing a severe reaction to a topical flea or tick medication; in those cases, one part of my treatment protocol was to bathe the animal to remove as much of the medication as possible. We do not have this option for medications given orally. These animals need to have their liver and kidneys detoxed, then supported. In my book, Yin & Yang 2.0 Nutrition for Dogs, you can use the Liver Support, Liver Draining, Blood Tonic, and Kidney diets. I also suggest the following supplements:

• Milk Thistle 50- 100 mg per 25lbs twice daily 

• NAC 500mg twice daily for 2 weeks, then once daily for two weeks

• Chlorella 25mg twice daily for 3 weeks

• The Chinese Herb Di Tan Tang for seizures 0.5 gm per 20 pounds body weight twice daily until the pet has been free of seizures for at least three months

• Liposomal Glutathione 100mg daily for a week

• Curcumin 100mg once daily for a week

• Broccoli Sprouts 100mg once daily for a week

• GABA (gamma-aminobutyric acid) 100 mg once daily for a week

• Add asparagus and dandelion greens or root to the diet. Dark leafy greens such as kale, beet tops, and spinach may be helpful.

• Epsom salt/baking soda baths to pull out toxins

• MCT oil 1/2 teaspoon per 10 pounds or 1/2 tablespoon per 30 pounds of body weight. Start slowly.

Some pet parents have continued these supplements for longer periods without adverse effects, even if the pet is still experiencing symptoms. If your pet is experiencing seizures, I have additional suggestions.  

What are the long-term effects?

In the cases so far, some animals have made a full recovery, while others have experienced permanent side effects. Using my protocol, I have helped improve the quality of life for many animals, but it is important to remember that the damage may be permanent. Some of my clients now have to deal with seizures or other neurological side effects for the rest of their pet’s life. 

With any animal that had any level of neurological or internal adverse reaction to these medications, I recommend keeping them as far away from chemicals as possible for the rest of their lives. This means using natural flea and tick prevention, asking for vaccine titers (blood tests to determine whether your pet has immunity to disease), or getting exemptions instead of vaccinations. These pets need to be fed a high-quality, species-appropriate diet made with human-grade ingredients.

Disclaimer: This content is for informational purposes only and is not meant to diagnose, treat, or replace consulting a primary veterinarian for individualized care.

Credit to: Dr. Judy Morgan. drjudymorgan.com