It's not bad. Nothing to stress about. I mix Tobi w/ Albuterol when I do my nebs and I have never had a problem. I've done them separate and together (both way of doing the neb was okayed by my CF Doc, no preference, it was up to me), to see if there was a difference in how it made me feel and there was no difference. Mixing doesnt cause a problem or chemistry change...so, dont stress. It will be fine either way.