Gabapentin 100mg Neurontin, gralise, horizant is a medicine used to treat partial seizures, nerve pain from shingles, and restless leg syndrome. It works on the chemical messengers in your brain and nerves. Gabapentin is from a group of medicines called anticonvulsants. Different brands of gabapentin are not interchangeable, and they are FDA-approved for different conditions. Use only the brand and form of gabapentin your doctor has prescribed. Check your medicine each time you get a refill to make sure you receive the correct form. Neurontin (gabapentin) is used to treat pain you may have from shingles postherpetic nerve pain. It is also used with other seizure medicines for partial onset seizures in patients 3 years and older.