What is the treatment you claim?
Wikipedia claims that "Treatment [for small fiber neuropathy] is based on the underlying cause, if any." Given that idiopathic means having an unknown cause, that seems to contradict your statement.
For severe cases, things like mexiletine can be used if you're willing to tolerate the side effects. Sodium-channel blockers like lidocaine + epinephrine can be used for localized treatment during sever pain.
It's a fuzzy distinction because SFN is almost always a sign of an underlying cause (even if unknown), and symptomatic treatment IS medical treatment.
(fwiw: I have SFN as well, not that it matters)
Gabapentin, Pregabalin etc can help with the pain, but not the underlying cause.
I haven't come across mexiletine before, but after a quick glance if looks like it's unlikely to be prescribed in the UK (I'm in the UK :).
I must have tried dozens of medications over the past 4 years or so, but it seems I have some dodgy genetics, as I can't tolerate most, or I have an atypical response (gabapentoids make me feel drunk, SNRIs nauseous, and tricyclics do absolutely nothing). I also tried topical gabapentin and capsaicin, but neither did anything.
> It's a fuzzy distinction because SFN is almost always a sign of an underlying cause (even if unknown)
For me it started when taking immunosuppressants for another condition - within a couple of weeks, the pain started and has been there every minute of every day for years since. I have 3 other immune-related conditions, one of which is rare, and I do believe all of these is related - but I'm resigned to the fact that I'll never find the underlying cause.
I did two rounds of it and decided it was a terrible medication. I could barely even walk (I distinctly remember my poor father helping me down some stairs at ikea the first day I took it, unknowing what was to come).
Eventually I found a rheumatologist that understood. She started me on 100mg Gabapentin in the evenings. I did that for 2 weeks. I slept better, which was nice.
Then I added 100mg in the morning with a dose of magnesium citrate. Gabapentin is absorbed in the lower GI tract and magnesium citrate increases intestinal motility. This effectively makes the 100mg dose therapeutically equivalent to 20-50mg.
After a week, I'd have my morning dose normally.
Then 200mg in the evening after a week. Then 200mg in the morning. Then 400mg in the evening... Etc...
It took me a little over 3 months to get to the appropriate therapeutic dose, but I managed without experiencing any unpleasant side effects. I then switched to Pregabalin without any titration, and it's more effective for me.
I spent at least 5 years rolling back and forth between pregab/gaba before a sensible doctor walked me through a tolerable process. Hopefully this might help you communicate a similar system with your healthcare professional so you can try it again.
It's been totally worth the effort.
I actually do take magnesium citrate daily anyway (200mg twice a day), but it didn't seem to help me here.
I even tried taking 2 weeks off work and took the minimum dose for the entire period - it was a horrible couple of weeks, where I felt drunk, dizzy, disoriented and anxious for the whole time. I just really can't tolerate them :( I had a similar experience with SNRIs, and also experienced horrendous withdrawals with them - I've tried about half a dozen of them, but after my last experience I accept they are not for me, and will never try another! I guess it all comes down to genetics.
Anyway, all that said, your advice seems good, and I'd encourage others to try to persist and slowly titrate up.
At some point after this happened to me, I switched to a low-carb diet (but not because of the SFN, because of a rare auto-immune condition; didn't make any different to the SFN pain, not that I expected it to).