You should take it two hours before with LOTS of water. The reason is this. Mucus provides a barrier that is not easily penetrated by medications. It is a sort of insulator. The albuterol sulfafe will penetrate, but it is better not to have this barrier to the medications. The same applies to use of Foradil. Using the expectorant before treatment optimizes the treatment.
Should not matter ..... I would take it an hour or so before your neb treatment so if it helps loosen up the mucus, hopefully the other meds will be able to improve the breathing even more. Hope that helps!