Protect your dog from the threat of potentially deadly heartworm disease with once-monthly Heartgard® (ivermectin) Tablets for medium dogs (26-50 lbs). Heartgard Tablets are approved for use in puppies as young as 6 weeks, small dogs regardless of weight, pregnant or breeding bitches, stud 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 Tablets are available only through prescription from a licensed veterinarian.)<P>Heartgard Tablets are 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.