This med is an oral version of lidocaine, it was used more widely in the past I believe, but if the side effects are tolerated can be very effective. I see neurologist Dr Robt Schwartzman from Drexel University in Philly, he is a leading researcher into RSD and other neuropathic disorders. I have full-body RSD due to a vaccine reaction, and one treatment he tried to put my RSD into remission was an in-patient IV-lidocaine infusion. I wasn't able to tolerate it; as the dose was slowly increased I became nauseous and the room started spinning. Despite pausing, then restarting from a lower dose, I wasn't able to continue.

I was sent home, though, with an RX for mexiletine, which I took for several months until starting a different treatment involving an even stronger med with a higher side-effect profile. I didn't suffer any bad results from either treatments or from the mexiletine. I think I got some benefit from it, but at the time my pain was just raging, so it seemed that nothing really touched it.
My Drs at home were not familiar with it's use, either, and may not have increased it to the desired dose for effectiveness, a drawback to being treated by Drs from away unfortunately.

I hope you see good results with it, and no side effects. Because of the treatments I've had, I am assured my heart is in VERY good shape, at least that's one body part that I can rest easy about!

beth