Hi Sue. Yes, I've been treated with Tobramycin three times in 2 1/2 years. Last time I was symptom free almost a year. The pulmonary doc I'm using now said that if I need to do Toby again because of pseudomonas that he will prescribe 2 weeks on and 2 weeks off. He never said for how long total after that. My previous doc at Emory did 28 days and done. I like the idea of two weeks but sure need to stay on it long enough to make a difference. I looked back on my specific notes during the Toby treatment I was on last May and honestly I don't think a two week period would have been enough. After the 28 days of treatment I submitted a sputum and it revealed "no growth of any pathogens."