Oral Flea & Tick Prevention Adverse Reaction

Some of you may have seen the recent video circulating on Facebook about the isoxazoline class of parasiticide used in oral flea & tick preventives such as Bravecto, Nexgard, Simparica, and Credelio. Social media can be a powerful communication tool. We all know that not all the information shared is completely true. The facts can be wrongly interpreted or distorted to sway the opinion of the reader. We understand the concerns, but before rushing to judgment we ask that you do your research and discuss it with trusted professionals. For your convenience, we have gathered information to share with you from Merck Animal Health (the maker of Bravecto) and the Food & Drug Administration.


As part of its regular monitoring of all pharmaceutical products, the U.S. Food and Drug Administration (FDA) conducted a review of the isoxazoline class of parasiticides. As part of this review, the FDA has issued a drug safety communication and has requested updates to the prescribing information of all medicines in the isoxazoline class – including Bravecto (fluralaner) – to include information about possible neurologic adverse reactions in the precautions section.

Adverse Reactions

Any time your pet has an adverse reaction, or an unwanted effect from a drug, it should be reported to both your veterinarian and the drug company. The event should be documented in the patient’s medical record. The drug company will gather information about the case and can make recommendations to the veterinary staff for the care and treatment of the patient. The drug company is required by law to share the gathered data with the FDA to continue to develop safety recommendations.

Merck Statement

“Merck Animal Health remains confident in the safety and efficacy profile of Bravecto, which has been established through comprehensive clinical research in more than 170 studies. After three years of post-marketing surveillance of more than 80 million Bravecto doses distributed in 85 countries, the overall worldwide reporting rate for neurological signs, including seizures, remains classified as very rare.”

Helpful Links & Contact Info:

 FDA Website

Bravecto Website

Merck Animal Health (Bravecto): 800-224-5318

Elanco Animal Health (Credelio): 888-545-5973

Merial (Nexgard): 888-637-4251

Zoetis (Simparica): 888-963-8471


Phone: 240-402-7002

Fax: 240-276-9115

FDA, Center for Veterinary Medicine

7500 Standish Place, HFV-1

Rockville, MD 20855

It is always recommended that pet owners speak to their veterinarian before administering any medications including flea and tick control products, heartworm preventives, supplements, and over-the-counter drugs. Recommendations for flea & tick products are tailored for your pet based on their health conditions, history, and lifestyle. Fleas and ticks transmit diseases and pose risk to both animal and human health making protection from these parasites critical.

If you believe your pet is having an adverse reaction to a medication, give Bemidji Veterinary Hospital a call at (218) 751-2753.

What's Next

  • 1

    Call us or schedule an appointment online.

  • 2

    Meet with a doctor for an initial exam.

  • 3

    Put a plan together for your pet.