Check for side effects of this antibiotic, you daughter is young and it causes different side effect in different age groups. My mother was on this antibiotic and it was the worst thing for her. See if you daughter can change to another antibiotic to help her in a more productive way. Antibiotics should not cause other health problems or discomforts.
Hope this helps....All the best to your daughter.
I am sorry that your daughter is going through all of this...Mycobacterium is just such a tough bug. What has her CF doc said about all of this as far as her wanting a short break from the meds? Those meds are just so harsh on the body...I know that anytime I am on multiple IV antibiotics, I just feel terrible all around...no appetite, joint pain, raw GI system the works. I too have an atypical form of CF...(I am a genetic mess!) and have not cultured MAC, but cepacia and other tough bugs. I feel for what your daughter is going through as far as the meds go and just having to do them for so long.
As far as inflammation, I am a fan of Ibuprofen..it seems to help joint pain along with hot showers, heating pads. I wish I could be of more help to you. Sunny