maxillary sinus infection

My father has been diagnosed with having a maxillary sinus infection. He has been taking medicine for about three months and does not seem to be getting better. Now he cannot taste or smell. He is on Flonaise,Sulfatrim,Doxycycilne, and Guaisenesin but it does not seem to be improving. He is a hard man to get to go to the doctor and I need to now how serious this may be. He lives in an area of Missouri where there is not much technology and I am trying to find help. Also let me include the fact that my father has no spleen and cannot fight infection.

[National Jewish]

When sinus infections do not respond to typical therapy there are usually reasons for this.  A couple of these reasons are:
1. The infection is due to a fungal infection and not a bacterial infection and therefore does not respond to conventional antibiotics.  The only way to determine this is with a specific fungal culture.
2. The opening of the sinus is blocked and therefore this functions the same as an abscess.  This can be determined by a CT Scan of the sinus, which can evaluate the sinus opening.
I would work with an ENT specialist to get to the reason for a lack of response.