I did Tobi one month on, one month off which is a standard regimen for the drug. After 2 or 3 years of that, I developed a resistance to tobramycin, which sucked because so many of the IV's for us to fight infection are based on tobramycin. Another reason why chronic prophalactic antibiotic use to keep our cultures down isn't a good idea in the long run. Unless it's something like collistin where it's supposedly impossible for your bugs to get resistant to due to it's properties vs either gram negative or gram positive PA. I personally think collistin is crap, I felt great on it for the first couple of times using it every other month, then after that it was about as effective as inhaling saline antibiotic wise.
My good female friend on her CF deathbed was trying to warn me about tobi somehow, but she couldnt talk and couldnt write to tell me what she thought.