JAV
I haven't seen studies for interactions among intranasal drugs; however, if you look at the Exubera label you'll see that they did extensive studies to examine not only interactions between inhaled drugs, but also the effect of intercurrent respiratory illnesses.
It only makes sense that drugs that affect the nasal mucosa, such as topical nasal decongestants, would affect the absorption of an intranasal drug. And speaking as someone who is getting over a cold, I'd expect that the abundant mucus I produced would also interfere with absorption.
These are relatively minor issues, though.
