What treatments are most effective for muscle cramps and stiffness in Isaac's syndrome and other peripheral nerve hyperexcitability disorders?

I believe that the most effective treatments for cramps and fasciculations/peripheral nerve hyperexcitability in Isaac's syndrome are (fast) sodium channel blockers such as carbamazepine and oxcarbazepine. We often prefer the latter due to fewer side effects. I have occasionally found mexiletine hel...