Let me start by saying that you will neither become addicted to nor immune to ibuprofen or any other non-steroidal anti-inflammatory (they are not regular pain killers - different class of drug), but they will help your side effects enormously. You just have to watch out for gastric irritation and possible ulcers - use them for one or two days a week, and always on a full stomach.
I used to be bothered so badly with side effects - I couldn't sleep, sweating, chills, fever, and muscle contractions so bad my husband had to help me 'unbend' or break the muscle spasms! Sweating big time!
I followed NHE's advice and started taking my shot earlier - I take mine around 3pm, with 4 to 6 hrly ibuprofen (800mg) and although I still experience side effects (wish I could stop taking the stuff but I haven't had a relapse since I have been on it and I was pretty bad before) - the side effects are not nearly so severe! So changing the time you take it might help - there is something about night time that just makes everything so much worse, the sweats, chills, pain...
He also suggested that I switch from the auto-injector to the powder form that you mix your self, and I think this also helped, and lastly, he suggested that I stop my combi-med (tylenol, ibuprofen and codeine all in one tab) and just take ibuprofen - and try a bigger dose, so I now take 800mg about an hour before I inject, then another 800mg at about 8pm, and 400mg at midnight, and 400mg or 800mg the next morning, sleep n a bit, and then I am fine. I find that 24 hours takes care of my side effects now. NHE is my Avonex guru!
If all your hormone levels are fine (menopause is very unlikely at your age, but you can have a simple blood test to check), then this is probably from the Avonex - night sweats are listed on the package insert.
Hope some of this helps - if you are inclined to implement any of these suggestions, I would suggest - move the time to some time in the day, change to the powdered form if you can (check with your doc), and use ibuprofen with a fairly heavy hand for 24 hours - doing all of this kept me on Avonex when I was going to stop - I felt like I wanted to die every weekend (drama queen)!
I know that this sounds really obvious, but I've been having a problem lately where I often miss the obvious things even though they're staring right at me.
I truly relate to this! I even open the fridge, stare blindly at all the stuff in there, and then end up closing it again because I haven't a clue as to why I opened it in the first place!