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In cats with chronic upper respiratory problems (that "snotty nose") I will usually put them on long-term antibiotics that can penetrate the bony sinuses as well as an anti-viral medication. The prednisolone is a good anti-inflammatory agent, but if there is a bacterial component to the problem (is the snot yellow or green in color?), then you need an antibiotic.
Many times chronic sinus problems are partly due to a herpes virus infection. I generally prescribe L-Lysine, 250 mg every 12 hours, until the problem has cleared up. You can buy lysine in 500 mg tablets at any pharmacy, or your vet may have a palatable paste available.
The antibiotics I prefer to use are either doxycycline or clindamycin, both of which can penetrate bone to where an infection can hang out and be difficult to eradicate. I generally start with 6 WEEKS of antibiotics, along with the lysine. If, after 3 weeks, there isn't much improvement, then I will add in an anti-inflammatory like metacam (but not a steroid which makes it harder for the immune system to fight off infection).
Hope that helps!
I was given medication for that bacteria twice, I can't remember the name, it was a rather large round medium browm color which helped only temporarily. I will try the L-Lysine