Does anybody out there have any advice for me? My family has given their horses the same de-wormer for 20 years and I have heard you need to change up the medication once in awhile to prevent the worms from becoming resistant. I have also heard that if the horse isn't accustomed to a regular schedule for worming that the initial dose should be half the recommended and followed a short time later (half the usual time) with a full dose. I have only been managing our horses health for a little over a year and have a lot of confusion. I catch them contradicting themselves around here and its always a 3 hour explanation of every detail associated when I ask anything. Please help a confused owner.