Gabapentin, sold under the brandnames Gralise, Gabarone, Fanatrex, Neurontin (and mmany others) was discovered in the 1970s, and was first used as a muscle relaxant and painkiller.
In the US alone, it currently has more than 40 million prescriptions per year.
It's used to treat, and (and many other conditions).
Its 'mechanism of action' - both as an anticonvulsant and as an analgesic - are unknown.
Further info Anaesthesia Volume 57, Issue 5