Phyl, my husband's ALS doc prescribed this drug in addition to the Rilutek. He did have diahrrea for a few months, but it seems to be levelling off now. It's hard to answer your question because according to our doc, the purpose of the drug is to slow the progression, so it's hard to know how fast it would be going without it, right? My husband's progression seems very fast to us, too. He was diagnosed in September and at that time was still able to get around slowly with a walker, and needed a little assistance standing up. Today, just five short months later, he cannot walk at all, cannot stand, and cannot use his hands well enough to feed himself! I've said it before, we feel like we are on a runaway freight train! So enjoy every moment you have, and like us, pray that Al has nailed it and he will plateau for a while! Hang in there and stay active in this group....these are great folks with a wealth of information, experience, and support!