Heartgard® Plus (ivermectin/pyrantel) for medium dogs (26-50 lbs) is a chewable, beef-flavored tablet administered once a month to protect your dog from the threat of potentially deadly heartworm disease, plus control against roundworms and hookworms.<P>Heartgard Plus is approved for use in puppies as young as 6 weeks, small dogs regardless of weight, pregnant or breeding dogs, and Collies. Dogs 6-months of age and older should be tested for heartworm disease prior to being put on a preventive program and tested annually thereafter. (Heartgard Plus is available only through prescription from a licensed veterinarian.)<P>Heartgard Plus is also available for small (up to 25 lbs) and large (51–100 lb) dogs. For dogs over 100 lbs, mix and match to reach the appropriate weight range.