Yikes. Yes, it happened to me yesterday. At first it was quite surprising. Unfortunately I woke up in a cranky mood so that did not help. My doctor came in asked me how I was doing today. I told him I woke up cranky. He stopped looked at me and asked why. We talked a bit about that and he informed me I could reschedule If I was not up to the shot today. As we talked and I became less cranky I stayed. He then told me about the medication change, he did explain it to me, why and what he hoped to achieve by this change in a calming compassionate way.
I did lots of my meditation breathing, the shot went well. The after effects of the shot were the same, no changes there. It did take me a few hours to process it all however I am good with it and no new worries.
I would definitely ask my doctor why the change. I have found doctors overall want to help up be informed and have good experiences. Once a doctor knows you are interested they are willing to help and remember to keep you up to date for next time. If I have questions I write them down because the appointment day I do not remember everything.