I have used Iverhard Plus for my first two dogs Reggie and Tasha. I just wished with all my heart that the people that owned Reggie before we got him would have. He came to us with bad heart worm. After our Vet worked with us we were able to get Reggie back on the right track and kill all the worms. I would never have a dog and not give him or her Iverhart Plus Heartworm. One of the best on the market. Quality of Ingredients Iverhart Plus is so easy to use one tablet a month and your done. All three of my goldens love the taste and they are made of the hightest ingredients.Iverhart Plus is also FDA approved and its made in the USA and that is one of he most important things I look for when buying for my dogs. I would recommend Iverhart Plus to any one who loves there pets and wants to do the best they can for them. Side Effects I myself have not found any side effects in any of my dogs from using Iverhart Plus. Iverhart Plus has done the job in protecting my dogs from any heartworm for more than10 years.