It could mean that it didn't work for them at the time. Every flare is different so even if the medication didn't work for this flare that doesn't mean it wont work in the future. I've had a resection and was on 4 different drugs at the time but I don't believe any of those meds failed me, it was just too far out of hand where nothing would work. I think people would say if they were allergic to it rather than saying it failed. I think what they mean is that they are currently in a flare and they tried a med and it didn't help enough or at all.