I think a phone call from your doctor will clear this up. All the drugs are discounted.

Beta 1b - betaseron, was approved first. In August 1993 (I drew number ~ 27,000 in the lottery for it). Beta 1a - Rebif and Avonex, came later. COP II - copaxone, I think came last in the approval process. And yeap, there was a COP I. There's also some 30 other drugs that were in trials at the same time that didn't make the FDA cut.

They all have roughly the same efficacy, so I can't see why an insurance company would lean one way or the other unless they're getting a skewed discount on any particular day.

Tom