postherpetic neuralgia
"I had many symptoms at first, especially imbalance, and drowsiness. I could never drive my car during the use of this medication. But overall, it helped with the sharp needle-like stabbing pain all over the area in which my shingles spread. I was worse case my doctor and neurologist had ever seen.  When the shingle scabs had fallen and my doctor said the episode was over, I had no pain. Then suddenly from nowhere terrific pain began to increase to the point where my doctor had to prescribe this medicine. I've only been on this medicine since June. It is now September and dosage has only been increased once ( to 1800 mg per day)."