I have felt similar from some of the sprays. One theory is that the medicine is changing the way your sinuses act, so you will have changes in the pressure in them as well as the pressure they cause in your inner ear. The panicy feeling is probably caused by the dizziness.
I suffered from vertigo, which was blieved to have been caused by this sinus issue (allergies?). My sinuses and ears are bothering me quite a bit the past few weeks and the vertigo is back, but not as bad as in the past.. Anyway, last year I went to a Neurologist in Chicago who specialises in vertigo and since I had also developed anxiety he told me that the panicky feeling I had was caused by the dizziness. It's not normal for us to feel off balance and the result is anxiety.
Good luck!
Jack