You are paying the ENT to make recommendations to you. It is up to you to make the decision for your child. If you don't feel comfortable keeping your son on this antiobiotic then don't.
However, there is something going on with him. The pharmicist is on the right track. Strengthening your son's immune system is a great prevention to using antibiotics and nasal sprays.
I don't know what vitamins you are giving your son and not sure if you need to "double up" on them but may need additional supplements. I use a probiotic (good bacteria) for myself and my family and it has helped tremendously. The antibiotic (when broken down anti=against bio=life) destroys bad bacteria but also the good bacteria. That is why a probiotic (pro=for bio=life) would be excellent in getting the good bacteria in his system.
Talk to your ENT and explain your concerns.
The probiotic I have is neither a vitamin or an herb it is good bacteria. Also, it gets into the lower intestine where 70% of the body's bad bacteria resides. Just an F.Y.I.
If you would like to know what I use, email me.
Good luck and hope he feels better!