I remember an article someone wrote back in the 50s/60/s about off label use of an Epilepsy drug (Dilantin) - for mood disorders. It was trialled in prisons for eg (double blind, placebo etc) and was incredibly successful as a mood balancer in helping distressed and violent inmates regain their emotional equilibrium (they reported being happy!), but no one was interested, including the manufacturers, presumably because more money was to be made for everyone from the newer antidepressants/valium etc - which seemed to be less effective.
A problem with Dilantin is that it causes "pseudo-lymphoma" in some people, including me. This sometimes seems to progress to actual lymphoma which (as I realized later) is associated with ME/CFS.
So I'm not sure that Dilantin is a good choice for us.