I haven't used adrafinil or modafinil since getting ME/CFS, but back in college, they were some of the nootropics i tried to help me study, so I can at least comment on the differences between the two. Since adrafinil is a prodrug to modafinil, they should theoretically have similar effects. In my experience, adrafinil felt much weaker and had more side effects than modafinil. I actually tried adrafinil first, and when I managed to get my hands on modafinil, I was blown away by how strong, clean, and consistent it was. That said, it seems like a lot of people in the nootropics community have had better experiences than I.
What could account for this variability? Maybe I was simply a poor metabolizer of adrafinil. Maybe in addition to being a prodrug, adrafinil has its own pharmacological properties that I was more susceptible to for whatever reason. It's also very possible that the adrafinil received was of poor quality (though I bought it from one of the more reputable nootropics suppliers).
All of these factors could be relevant to you, though probably the only way to know for sure is to try it yourself. It's probably not particularly dangerous to at least try adrafinil if you know you tolerate modafinil well. There are very few reported health effects - mostly reversible side effects such as nausea or headache. Some people have reported increased liver enzymes from long-term use, so it might be a good idea to supplement with milk thistle extract or something while using it.
At least in my case, it always seemed like a bad idea to use psychostimulants for my ME/CFS, but I've read some people, especially milder cases, see some benefit from it, which I suppose is true for you if you're looking for a modafinil replacement. I'm curious, did you find that modafinil had a beneficial effect on the disease process itself, or was it more a practical tool for overcoming the fatigue, a sort of 'band-aid'?
