I've heard of beta blockers, specifically propranolol, being used in this way in an experimental PTSD therapy protocol, I think back in the 80s or 90s. It didn't seem to go anywhere, or at least I stopped hearing about it.

This 2016 metareview suggests the reason is insufficient evidence of efficacy, for that and a couple of other anxiety indications: https://pmc.ncbi.nlm.nih.gov/articles/PMC4724794/