My pain Dr had discount cards for Gralise when I first tried it. It still cost me money that wasn't an out of pocket expense for insurance purposes. Not sure if it would help but here is a link.
http://www.gralise.com/patient/resources
It took at least a year to get my health insurance to cover it. Sadly its probably up to your Dr fighting the insurance company to get them to approve it.
Good Luck