Did they not retest you after the Meropenem? Wondering why your pulmo only wants you to use Toby now for 3 months straight? He probably wants you to follow up with the Toby to be sure. I have read that the Meropenem is for the Pseudomonas in the lower lungs but the Toby gets the upper respiratory better. At any rate Pseudomonas is very hard to eradicate so perhaps you still have some and he feels that will kill the rest? Usually Toby is used to just manage Pseudomonas. To knock it back. So they prescribe it 2 weeks on and 2 off or 28 on and 28 off as an ongoing prophylactic treatment. I have chronic Pseudomonas so my pulmo wanted me to try it. I only lasted a few days on it. I lost my voice and appetite, felt bad but worse thing for me was decreased urine output (which is not supposed to happen with the inhaled version but it did). But some people do ok on it. I have been very interested in trying Meropenem. I have read good results from several people on the forum. Did you have any side effects from it?