My dogs have been on Simperica for years and never had any issues I have a 3 of dog up to a 120 of dog 6 in total and I\'m so happy I found PB ... Same product and a lot cheaper. I do advise getting a dose from your vet and talking with them and trying it before you buy in bulk or from the UK but it works well with my yorki, Maltipoo, German Shepherd, and 2 pit bulls and toy poodle all weights and sizes have done well for years