Amazon Basics Topical Flea Treatment for Medium Cats (5-9 pounds) prevents and kills fleas. Previously known under the Solimo brand, this cat flea provides the same effective formulation in a 4-dose pack. Our topical flea treatment for cats begins eliminating fleas as soon as 12 hours of application, including eggs and larvae. Active ingredients Imidacloprid and Pyriproxyfen work together to prevent flea infestations. For best results, apply these cat flea drops directly to the dry skin on the back of your cat, between the shoulder blades, on a monthly basis. This flea treatment kills and prevents fleas for up to 30 days after application