I was out of Advantage and borrowed a tube of Hartz for my cat from a freind. Bad idea, long story short, we ended up @ the emergency vet around 6 the next morning. Molly having seizures the whole way there in my arms! Why this product is on the market is beyond me. My vet as well as emergency vet both say adverse reactions are common. What’s wrong with this picture. I think all veterinary offices should display info on this subject for patients. How many pets need to go through this. The lucky one’s make it. Still waiting to see how Molly’s story ends.