Hi there Bobby Jean,
Welcome to the HealingWell Depression forum. I am very glad that you have joined us. I did find something on the net for you to read.
http://www.webmd.com/multiple-sclerosis/guide/ms-depression
There may be some good information for you there. I am sure that both MS and depression kind of go back and forth between eachother. You are a good friend to come here to get information for your friend.
Have you thought about a psychiatrist? And then a good psychologist? There are other meds to try yet, so don't give up on that. But a good psychiatrist could get a grip on what would work for your friend. And then recommend them to a good psychologist for some extensive sessions.
I am sure that others will be along with some advice for you. Just being there for your friend says a lot. You are a wonderful person.
Has he ever tried a mood stabilizer? I take abilify and it really helps me. Mention that to him. There are other types of mood stabilizers too.
Hugs, Karen