I switched to comfortis a while ago when every drop on i tried was not working.
it has worked a treat, have never had any bad reactions.
I'm a big fan
the recommended dosage is 1 tablet per month, however i found i gave her 1 a month for the first 2 months but after that 1 tablet lasts 6 - 7 weeks.
"He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion" Author Unknown