I thought I'd take a chance on buying a generic on the consideration that active ingredients are active ingredients. Shortly after giving my 7 year old golden retriever MilbeGuard, we noticed she was drooling from the left side of her mouth. A few days later she couldn't blink and the left side of her face was drooping. Every doggie parent knows the drawing of their lips that occurs during muzzle dueling, and my dog's nose pulled entirely to the right and her left side remained as though paralyzed. I brought her to the vet and after blood work and x-rays we found no injury or illness explaining this. The only change was the addition of MilbeGuard. When I contacted Ceva, the representative (who was very professional) informed me that they would work out a return for the 2 years supply that I had purchased (1 year each, 2 dogs), but that it wasn't typical to cover vet bills for stated side effects (Ataxia being a stated side effect and I guess close enough to facial paralysis). I accepted that at the time since the only suggestion that MilbeGuard was the cause was the stated side effect and the appearance shortly after taking it, but said to go ahead and run it up the flagpole for potential reimbursement because, why not? I followed up a little later and was informed that Ceva had denied the reimbursement in part because MilbeGuard has a short half life. This stuck out because my dog's symptoms had been improving starting at about 2 weeks after taking MilbeGuard and a week or so after the first symptoms appeared. Initially it was infrequent blinking and eventually control to her left lip returned. While this is still correlation, it's more like the correlation between seeing a wet street in the morning and knowing a storm was predicted overnight. I may not have seen it directly, but all the events and timelines point one way. I followed up to confirm their FDA number to report the interaction and apparent injury and haven't gotten a reply yet. I will not be buying this again since saving $70 on a year's supply got me a dog that still doesn't blink regularly and a $550+ vet bill. Full disclosure - I bought the product from my local vet, not Petco and this dog has had Sentinel which has the same active ingredients in the past. Coincidence that this naturally happened without physical explanation is entirely possible, but it would be one heck of a coincidence