I have a similar story, with an antibiotic that is also an immunosuppressant (I was taking it for that effect). After taking it for just 2 weeks, I had terrible pain in my arms and legs. My doctor suggested I keep taking it for a couple of weeks more, to see if it went away. It got worse, and I stopped it a week or so later. I understand this is a very rare side effect, so rare I don't think it was even mentioned in the leaflet - I'm just incredibly unlucky to have such a reaction.

I was left with small fiber neuropathy (nerve damage) in my arms and legs, and with CFS (Chronic Fatigue Syndrome) too. This means I'm in constant, unending pain (which takes a huge mental toll), that I'm tired all the time, and if I do any more than the gentlest of exercise, I fall asleep and am more tired and in even more pain for days or even weeks afterwards. It's fucking horrible.

This was about 6 years ago, and I'm pretty sure it's permanent. I haven't quite given up hope though - I have several Google Scholar alerts setup, and read several papers every week, in the hope of finding something that might reverse things even a bit.