Tegretol is evil stuff for some people. When I was on it, it took a while to get to a dose that had any impact on my pain, but when I raised the dose some hideous side effects kicked in.
I've read the 'may cause drowsiness' label on medication before but I've never been physically unable to keep my eyes open in a busy place in the middle of the day before.
My kids thought it funny that I had to walk them to school once looking as though I was drunk when the tegretol kicked in and I could not walk in a straight line.
And it gave me a huge twitch. I couldn't write or type without my wrists jerking violently, and when it first happened, I was driving and it made me let go of the wheel.
I went straight back to the gp and they put me on gabapentin instead and it's been a game changer for me.
I'm 6 years in with TN and find I can lower my dose on good days, but not drop it completely. I once asked the doctor how long I should take the tablets for if i thought I wasn't getting any symptoms. His answer was ...."Ages" as it's a relapsing and remitting pain issue and it takes a while for the drugs to get to a reasonable level in your system. So the advice you got to take it when you have pain and then stop is flawed, but a lot of GPs don't understand TN well.
My friend, however, had TN before me, but then has been in remission for 5 years! (Bitch!
).
I had the mri and the lumbar puncture in case it was MS and was clear, but they did find the compression in my brain that causes the TN for a lot of people.
I'd recommend going back to the gp, asking to try something else so that you can have and maintain a low dose if it gives you no side effects, then you'll be at a level that you can easily raise if and when you get symptoms.
I'm on 1 or 2 x 600mg a day, and I take the full 3 a day when I have flare ups. One big trigger for me is exercise and when the gym opens again I'll have to go back up to my 3 a day.
Good luck with it.