After giving half the recommended dose for my kitten of Hartz’s roundworm medicine, my otherwise healthy 8 month old kitten had a horrible seizure. After frantically taking Loki to emergency vet and $210 later, he his stable. Loki presented signs of classic intake of toxins. No signs of ingesting of any other poisonous substance, i.e. mouth sores or gastrointestinal abnormalities. Vet tech said they see this frequently from OTC Hartz products. It seems we were lucky enough to still have our our furbaby alive after ready some of the posts on this page.