Advantage Multi for Dogs is a topical solution. See steps below for how to apply. Step 1: Remove one dose applicator tube from the package. While holding the tube in an upright position, remove the cap from the tube. Step 2: Turn the cap over and push the other end of the cap onto the tip of the tube. Twist the cap to break the seal, and then remove the cap from the tube. Step 3: Part the hair on the back of the dog between the shoulder blades until the skin is visible. For dogs weighing 20 lbs. or less, place the tip of the tube on the skin and apply the entire contents directly on the exposed skin at one spot between the shoulder blades. Step 4: For dogs weighing more than 20 lbs., place the tip of the tube on the skin and apply the entire contents directly on the exposed skin at three or four spots on the top of the backline from the base of the neck to the upper back, in an area inaccessible to licking.

Talk to your veterinarian about the heartworm testing that is recommended before starting your dog on a heartworm prevention program.