I had huge probelms with getting my Colistin approved too even though I am resistant to all other antibiotics and the CF clinic and doctor tried everything they could! I have Medicare and Medicaid. For a while I was getting it through Foundation Care but they don't take Medicaid and they said I no longer could get it from them b/c Medicare denied it. A guy from Carter's Pharmacy in Jacksonville, FL started working with the Adult CF Program and Medicaid so they could get people qualified for the e-Flow and Colisitn. Well, that worked for one month then Medicaid wouldn't cover it but the guy at Carter's Pharmacy was able to find another Medicare Plan that would cover the Colistin. I did have AARP and now I have Community CCRX Medicare Prescription Drug Plan and so far it has been approved! The owner of Carter's, Greg Carter, has been very helpful and done a lot to make sure I got my medication. If any of you still have problems, look them up. They are a mail order pharmacy. Here's their number in case you want to call 1-800-557-0583