I have dogs that weigh 50+ lbs and have to give 2 of the regular diphenhydramine (25mg) at a time. These are much more convenient in that I can now give just one instead of two every time. They are a big help with a dog that was having allergies when everything started growing & blooming and had to have them every 6 hrs. I also have another that gets carsick but he doesn't if I give him these before taking him anywhere. The only disappointment was that they still have to be given every 4-6 hrs - they aren't time release to last longer. I was really hoping for something to get my itchy one through the night without giving them at 3 am.