NexGard for Dogs 4-10 lbs, 6 month supply is a once-monthly flea and tick preventative. NexGard contains a brand new ingredient not used in any other flea and tick protection, Afoxolaner. Afoxolaner allows NexGard to continue to provide effective treatment for a full 30 days. Effective against and the American dog tick, the black-legged tick and the Lone Star tick 48 hours after treatment. Nexgard is dispensed with the package inserts and instructions but does not include the box.