Click Here for Application DirectionsClick Here for Warning InstructionsFor the treatment and prevention of fleas and ticks on dogs and puppies from 8 weeks of age. FRONTLINE Plus Large Dog 20 - 40kg Tick & Flea treatment combines fipronil, the active ingredient in all other FRONTLINE products, with (S)-methoprene, an insect growth regulator. This combination effectively kills fleas on the pet, and breaks the flea life cycle by inhibiting the development of flea eggs and larvae.