Update: K9 Advantix II vs. Advantage II

I’m sharing this Facebook post from my husband’s friend. Even though I have not personally had any problems with K9 Advantix II, this story scares me. I talked to my husband about it, and we’re switching Tessie to Advantage II since she is a small breed dog. It might be wise to switch Casey to Advantage II as well because of the ingredient Permethrin being linked to cancer in dogs. Or, ask our Vet about more expensive oral flea-prevention treatments.

Please talk to your Vet if you use K9 Advantix II. Is this just a rare case, or should all pet owners be concerned? Watch for a future post about natural ways to treat fleas & ticks.

Side Effects from Drugs.com
Monitor your dog after application, Side effects, although very rare, may include signs of skin irritation such as redness, scratching, or other signs of discomfort. Gastrointestinal signs such as vomiting or diarrhea have also been reported. If these or other side effects (such as lethargy) occur, consult your veterinarian or call 1-800-422-9874.


I applied K9 Advantix II to my 20 pound Jack Russell/Rat Terrier mix for the first time on Sunday night. Previously, she had used other topical treatments such as Frontline. After seeing that Advantix has more coverage than Frontline, I decided to give it a try. All seemed fine until Monday afternoon when she started having severe vomiting/diarrhea issues. We gave her some Pepto and Amoxicillin as advised by the Vet, but she has just gotten worse since with her temperature dropping below 99 degrees. Finally about 26 hours after initial application, she had to be seen by an Emergency Vet as she had soiled herself and was unable to move, bark, or even blink. After having lab work done and paying nearly $1,000, we found out her kidneys are starting to fail. The Vet has put her on an IV for 48 hours at which time we will reassess her creatinine levels and see if the severe dehydration had anything to do with the concern of her kidneys. Mind you, I have had this dog for almost 9 years with regular vet checks (the latest being May of this year) and she has never had any health concerns at all. Also, she is only outside to use the bathroom with my supervision, and then she immediately comes back inside. This product had the best reviews; but after looking up adverse reactions, I’ve found tons of cases where dogs (usually toy/small breeds) have had neurological damage, seizures, strokes, vomiting, diarrhea, and even death as a result of this topical treatment. The cause seems to be the high levels of Permethrin in the treatment (which is advertised by Bayer as being highly toxic for cats by the way. This should be a red flag as is). I am putting this story out there in hopes that other pet owners (and lovers) will share the message and be warned that K9 Advantix II is absolutely not safe for dogs!! Tons of info has linked this pesticide to cancer in dogs as well. This was my first and last time using this treatment. The vet also said that kidney issues like this usually don’t just happen out of nowhere, and she had been 100% fine before the treatment. Now, I will spend the next two days hoping and praying that my dog will make it through the immense amount of pain and suffering she is in. Please share this post and make it go viral so other dogs won’t have to suffer like Sadie is.


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