I use Confortis for Spookie. We have fleas here, year round. I bought the 2-10 pound size, and cut them in half. One month I gave her a whole one, and her heartworm at the same time, and she acted a little off for a day or so. I think it was too much meds at once, and went back to 1/2 Confortis and she was ok. I think I'd go with 1/2 the first month, and if you still see fleas, increase to a whole one next month.