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Why I won't take clients who give oral flea meds to their pets...

Updated: Nov 29, 2023

Through out the years I've encountered multiple negative side effects in clients, friends, and neighbors dogs that were given oral flea meds. In my perspective giving your pet a toxic substance to ingest every month to kill a flea that might jump on them is not something that sits well with me. Prevention is something I've always worked on in training and my pets health. A healthy diet is a way to prevent disease, fleas, negative behaviors.

A few examples of experiences: A friend gave a dose or oral flea medication to her dog and it immediately had a seizure. A friend gave it to her cat and it displayed uncontrolled movement, lethargy and drooling. A client gave it to a very hyper anxious dog she just rescued and needed training help with for his extreme separation anxiety, when I went there the dog was lethargic, had vomited and had diarrhea and was completely not himself, we were able to leave the apartment with the dog not reacting at all, he was so sick from the medication we couldn't do any work with him. A neighbors dog lost the ability to walk (ataxia) after giving oral flea meds to his dog for years, he spent thousands of dollars at the vet trying to find the cause for his dogs inability to walk and looked up adverse reactions of the medication and found that this is a side effect. I had a client give a first dose two both of her young dogs and one died immediately, believed heart attack, the client didn't have a necropsy done to determine the cause of death, but since there were no other factors and dogs have been known to die from these meds, I'm assuming that the oral flea medication was the cause. I've seen dogs become more aggressive and agitated on oral flea meds and this is detrimental to working with a dog on behavioral issues.

I won't take on the liability of a dog on these drugs under my care as it's so hit or miss if/when the dog will display a reaction. I can't work with dogs if they are under the influence of a drug that causes these reactions, it's like Russian roulette for some dogs it's an immediate reaction and for others it can take weeks/months/years (the dog that all of a sudden couldn't walk at 6 years old had been taking it for years).

What I do with my dogs:

I use topical flea meds Revolution (vet prescription is needed to make sure you are getting the actual product and not a knock off) and Sentry Natural Defense, Isopropyl Myristate is the active ingredient for Sentry and it's not toxic like Sarolaner which is the insecticide in the isoxazoline group that's in Simparica and other oral meds. I've been told by vets that the topicals don't work anymore, but for me they do, I don't dose my pets every month and allow them to build up a resistance to it. Topical flea meds are still toxic and there have been adverse effects for dogs that have used them too, but in my experience, they have less dangerous side effects than ingesting it like the oral drugs. I have not had any dogs display adverse reactions to topical flea meds and have been using them on and off for years.

I use a good old fashion flea comb, baths and topical sprays (Wondercide). I use topical flea meds that is put directly on their skin when needed (Revolution and Sentry rotated), but spread out the application times of the doses out as long as possible (vs every 30 days like the product says), since they can build up a resistance to it.

I also feed my dogs as healthy as possible and don't feed kibble or give a lot of processed treats. A good diet is preventive care in many areas of a dogs life and with flea prevention it seems to be a factor too. I've rescued many dogs that were sick and have seen their overall health improve with diet and detox.


Project Jake:

Below is a copy of an independent study on oral flea medications that I suggest everyone to download and read. Pet owners need to make an informed decision when giving these to their pets...

safely evaluation of afoxolaner
Download PDF • 228KB


If you google does Simparica, Bravecto, Nexgard kill dogs, you will find news stories and personal stories of the adverse effects suffered by pets who were given them. There are numerous facebook pages w/videos of peoples dogs displaying negative reactions after they gave a dose to their pet.

There are ways to detox the toxins from the body if you have given them to your pet and are worried about the affects. I recommend contacting a detox specialist for pets if this is something you are concerned about.

The below is copied from the insert (most people don't read these) of the oral flea med for Simparica:

Mode of Action The active substance of SIMPARICA, sarolaner, is an acaricide and insecticide belonging to the isoxazoline group. Sarolaner inhibits the function of the neurotransmitter gammaaminobutyric acid (GABA) receptor and glutamate receptor, and works at the neuromuscular junction in insects. This results in uncontrolled neuromuscular activity leading to death in insects or acarines.

Abnormal neurologic signs such as tremors, decreased conscious proprioception, ataxia, decreased or absent menace, and/or seizures were reported in dogs receiving SIMPARICA (see Animal Safety).


Sarolaner is a member of the isoxazoline class. This class has been associated with neurologic adverse reactions including tremors, ataxia, and seizures. Seizures have been reported in dogs receiving isoxazoline class drugs, even in dogs without a history of seizures. Use with caution in dogs with a history of seizures or neurologic disorders. Post Approval Experience (2019): The following adverse events are based on post-approval adverse drug experience reporting for SIMPARICA. Not all adverse events are reported to FDA CVM. It is not always possible to reliably estimate the adverse event frequency or establish a causal relationship to product exposure using these data. The following adverse events reported for dogs are listed in decreasing order of reporting frequency: Vomiting, tremors, lethargy, seizure, diarrhea (with and without blood), anorexia, ataxia, pruritus, hypersalivation and hyperactivity.

Animal Safety In a margin of safety study, SIMPARICA was administered orally to 8-week-old Beagle puppies at doses of 0, 1X, 3X, and 5X the maximum recommended dose (4 mg/kg) at 28-day intervals for 10 doses (8 dogs per group). The control group received placebo tablets. No neurologic signs were observed in the 1X group. In the3X group, one male dog exhibited tremors and ataxia post-dose on Day 0; one female dog exhibited tremors on Days 1, 2, 3, and 5; and one female dog exhibited tremors on Day 1. In the 5X group, one female dog had a seizure on Day 61 (5 days after third dose); one female dog had tremors post-dose on Day 0 and abnormal head coordination after dosing on Day 140; and one female dog exhibited seizures associated with the second and fourth doses and tremors associated with the second and third doses. All dogs recovered without treatment. Except for the observation of abnormal head coordination in one dog in the 5X group two hours after dosing on Day 140 (dose 6). There were no treatment-related neurological signs observed once the dogs reached the age of 6 months.

In a separate exploratory pharmacokinetic study, one female dog dosed at 12 mg/kg (3X the maximum recommended dose) exhibited lethargy, anorexia, and multiple neurological signs including ataxia, tremors, disorientation, hypersalivation, diminished proprioception, and absent menace, approximately 2 days after a third monthly dose. The dog was not treated, and was ultimately euthanized. The first two doses resulted in plasma concentrations that were consistent with those of the other dogs in the treatment group. Starting at 7 hours after the third dose, there was a rapid 2.5 fold increase in plasma concentrations within 41 hours, resulting in a Cmax more than 7-fold higher than the mean Cmax at the maximum recommended use dose. No cause for the sudden increase in sarolaner plasma concentrations was identified.

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