When medications are first developed, they are usually developed to treat a specific issue. Once the medication is approved for use for that issue, doctors and researchers sometimes notice that other problems may improve when they prescribe the medication to their patients. For example, if a patient is taking a medication like Neurontin (gabapentin) for seizures, but he also had shingles that left behind post herpetic neuralgia, nerve pain, he may find that the medication not only is controlling his seizures, but is controlling the pain. Sometimes the discovery is intentional, sometimes it’s accidental, but when doctors find a different use for a medication, they may be tempted to try it since it is already available.
Somewhere along the line, researchers and doctors discovered that gabapentin not only treats seizures, but it helps manage the nerve pain from shingles and may also help the pain from fibromylagia.