neuropathic pain
"I had been having severe, migratory joint and muscle pain, along with horrific idiopathic itching. We tried everything (anti-histamines, steroids, etc) with no effect, finally trying gabapentin. It was like a miracle: the joint pain and terrible itching went away. However, I developed secondary pain--a deep, horrible ache in both thighs. It took me two months to even figure out that the pain in my legs was caused by the gabapentin (first of all, I suffer from RA, so pain is common; second, gabapentin is supposed to help with pain, not cause it, so this was confusing).  I went off the gabapentin (note: always consult a physician and taper down!), and sure enough, the debillitating thigh pain that I'd been suffering so long went away."