Modafinil is, strictly speaking, only licensed for narcolepsy. But neurologists used to be able to prescribe it ‘off label’ for MS fatigue.
The problem is that it apparently caused cardiac problems in some people so neurologists became unable / unwilling to prescribe it for fatigue. It was also becoming abused by people without medical need of it who wanted the extra sharpness it brought to their cognition (eg students doing exams).
But some neurologists are still finding ways of prescribing. If you get it, be aware that for the first few weeks it can cause a sort of teeth clenching edginess, I also felt quite nauseous. But after a month, I had no side effects at all.
As Alison says, if you’re offered it, take it. It does work. And it’s miles better than Amantadine.