A tasty, chewable tablet, Sentinel for Dogs make it easy to keep your dog protected against fleas and other parasites, including heartworm, for a month. Sentinel for Dogs is an easy to use solution for managing parasites in dogs and helps to keep dogs free of infestations of numerous pests for up to 30 days with a single dose. The medication is available with a prescription from a veterinarian and can be safely given to dogs at least 4 weeks old that weigh a minimum of 2 pounds. One of the two active ingredients in the drug is Milbemycin Oxime, which kills adult hookworms, roundworms and whipworms and also eliminates heartworm larvae. Lufenuron is the second active ingredient and kills flea eggs, causing existing flea infestations to eventually die.