The FDA recently issued an alert regarding products like Nexgard, Bravecto, Simparica and Credelio.  Here’s what you should know.


The FDA recently released an alert that reads: “The FDA considers products in the isoxazoline class to be safe and effective for dogs and cats.” but went on to warn pet owners and veterinarians about potential neurological reactions to the isoxazoline class of drugs.  According to the FDA, the alert was issued to help veterinarians and pet owners make informed decisions when choosing flea and tick products for pets.







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Adverse Reaction Rate (<1%) Has Not Changed Since FDA Approval


To be clear, the FDA alert is not in response to an increase in the number of reactions to this class of drugs. The number of adverse reactions (<1% at higher-than-recommended doses) has not changed since the FDA first approved these drugs for use.   The FDA statement is only designed to increase awareness.


For our part, we have always prescribed these drugs according to the FDA approved dosing recommendations made by the manufacturer, none of which have changed since the medication went on the market


In Drug Studies, Reactions Were Limited To Overdoses


In pre-FDA- approval studies of these drugs, it was only patients that were dosed 3 and 5 times the normal amount of the drug that had neurological reactions.  All reactions were self-limiting and resolved on their own without treatment.  All patients in studies were under the humane and responsible care of veterinarians.


The most common reported side effect of these drugs is not neurological issues, but diarrhea, vomiting, lethargy and lack of appetite.  Side effects are rare, usually only occur within 24 hours of dosing the patient, and are self limiting.


No Reported Neurological Side Effects Reported By Our Clients


At our practice, we have had no reports of tremors, seizures or any other neurological reaction to this class of drug.  A few of our clients (less than 5) have reported that their pet vomited their dose.  Most of our veterinary team members, including all of our doctors, use isoxazoline medication for preventing fleas on their pets.  We never prescribe isoxazoline class drugs to patients who have a history of seizures.


Pet owners should not be discouraged from using veterinarian-prescribed medications to prevent fleas and ticks on pets.  The risk of flea or tick infestation, and the diseases associated with both are much higher and more concerning that the very low risk of self-limiting reactions to isoxazoline medications.


If you have experienced any issues with your flea and tick product, please reach out to us for our advice.  You may also use this FDA Pet Owner Fact Sheet for more information.


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