Skip uses avicel, which is wood cellulose.
One thing about LDN that differentiates it from other drugs is that it is only in your system for a few hours. The low dose, taken at bedtime, stimulates endorphin production. The benefits people experience are from the increase in their own endorphins, not LDN itself.
I've been taking LDN since 2005. I started at 3 mg, increased to 4.5, had some increased spasticity with that and went back to 3 mg.
It isn't the only drug I take for MS. I also take Copaxone, and Estriol. I had some definite progression while on "LDN only". However, I stay on it because it improves my bladder and bowel control/function, my energy levels, my mood and my metabolism. There's also no way to know how much progression I would have had if I weren't on LDN.