I'm with Patrick123. The problem with the tooth is making the mg worse. As your immune system ramps up to try and handle the infection, it also makes more T-cells that make the mg worse. If you get the infection taken care of, it can only help the mg. As far as local anesthesia, I had a root canal done with 2 sessions of local anesthesia and had no problems. I don't recall the exact drug used, but my research indicated that there were no specific local anesthesia that would aggravate the mg.

Good luck with the extraction and hopefully, it will help with the mg.