i have done it, but i don't have a ton to offer on the subject. it doesn't cause and side effects for me, but it also doesn't really work. the first time i used it it worked so-so, and i had an improvement (coupled with the tobra iv), but it took longer than usual. the second time i used it was last month, when i was on ivs for 6 weeks. it was going to be 3 weeks tobra/mereem, then 3 weeks tobra/aztreonam, but within a few days of starting the aztreonam i started feeling cruddy again and we discontinued and went back to the merrem a week and a half into it. obviously that's just me though - it doesn't say anything about aztreonam as a drug.
i will say this: azli, the inhaled stuff i'm on, is NOT the same compound (although obviously the aztreonam part has some overlap). being sensitive to one does not mean you will be sensitive to the other. azli works great for me - iv aztreonam, not so much.
also, i have always discontinued the inhaled version of a drug when on the iv version, including both aztreonam and tobi. i'm not sure if that is just my doctor's favored method of attack or if there is a more universal reason why you shouldn't overlap drugs. i would say ask your doctor on that one.
good luck!