Hi Pixie. I have heard that novocaine has something in it that also raises our adrenaline level. This is to speed up the numbing process by getting our blood moving faster (or something like that). My mother and I are both very sensitive to it, and while we don't get full panic attacks, we both deal with heightened anxiety during dentist visits, even though we aren't afraid of them either.

This could be a very likely reason you had a panic attack during the filling. Of course, panic attacks are perfectly capable of coming out of nowhere too, which is always fun.