I Have Been Taking Benicar 40 For Years And Recently

I have been taking Benicar 40 for years and recently my insurance changed me to the generic brand olmesartan medoxomil. Is there a difference in the brands. Lately I have been struggling with loosing my voice. It is over 3 weeks I am having this problem. I saw an ent doctor and he said my vocal cords were very red and I did not have any infections. My voice seems like it is getting better for a day or 2 and then I regress . Also I have been having difficulty getting asthma under control and experiencing a dry cough. Can this change be related to the change in my prescription?