Some insurance protocols will cover the rarer drugs if more common ones are unsuccessfully tested first. But then the protocols are often wooden. Even if the patient has tested the unsuccessful drugs in the past, they have to be tested again, once on a particular policy.
That is the way it was. My insurance quit paying for an inhaler, sent the doc, me and pharmacy letters telling us what I was to take. It was not even top tier in 2013 while they were paying for it.