Is there any formula of Advantage flea medicine that is safe for both dogs and cats?

I have both a cat and a small dog? I need to buy flea medicine for both of them. I have scoured the internet for answers for what brand is best and of course everyone has different opinions but I think I have finally decided on Advantage but was wondering if any formula was safe for both of my pets so I wouldn't have to make such an investment in one day both because money is tight and I don't want to find out that is doesn't work for my pets and be out so much money.