Valleyvet.com Several forms of iver and fenben. I get the horse paste because it is easy to dose based upon body weight. They have liquid form too. Maybe it is more concentrated. It is my understanding that people do take iver and fenben at the same time. I find that 15000 iu of D3 and 3k of vite c daily help very much to just feel better. and the zinc you need w iver. But zinc must be with a meal or it gives upset tummy.