Hey, I've been on Septra (Bactrim) for almost a year and a half, and have not grown MRSA in my lungs in over a year. My Dr attributes this to my being on Septra all the time. It's like Azithromax, but a maintenance drug for MRSA but my MRSA was eradicated! It is possible to take this long-term with some nice perks! I've had no side effects from taking it.