I believe that medication starts losing its potency the older it gets. But with that said I have taken Tylenol and other things after expiration dates and they do work. A pharmacist can answer your question about potency. However.....you need to see your doctor. Did you wean off it like every other day as Gabapentin must be weaned down to avoid side effects. I take 900mg at bedtime. If Your Dr. put you on it did you let them know you wanted to stop taking it because yes, your symptoms can come back as Gabapentin addresses nerve pain. I use it for sciatic pain when my piriformis muscle acts up and gets inflamed and then sits on the sciatic nerve. Gabapentin cannot be just stopped and must be weaned down. I don't know why your Dr. put you on it but please give them a call or send a message to them if you are able so they can address the issue.