My dad had a heart attack about two years ago, he was put on several heart medications, one of them being Metoprolol. Recently he went in for an exam and his blood work showed that he wasn't getting enough oxygen due to sleep apnea. When he went back to the doctor he took my dad off of the Metoprolol and put him on Carvedilol and Lisinopril-- would anyone be able to tell me why the doctor would do this? My dad wasn't very specific about what the doctor said- I'm aware that Metoprolol and Carvedilol are both Beta receptor blockers but why the change? what's the cause of getting rid of the first prescription and combining two new ones?