That is a good question. I think Camzyos starts working very quickly. Within the first week I felt I was handling hills and the stairs a bit better. Two weeks I definitely felt that it was working and each successive week there has been progress. It has been exactly one month and I am back to my morning walk (2.5 - 3+ miles) at a very good pace and able to walk up hills without slowing down or stopping. I can go up and down stairs all day long. However, after two weeks I started to feel tired to the point of feeling like I needed a nap in the early afternoon. I have only been on it for a month and my dose has just been changed from 5 mg to 2.5 mg which is probably a good idea. The Verapamil that I was on has the same drug interaction concerns as your Diltiazem.