sore throat

I have been taking oral sulfazine for Rheumatoid Arthritis for 8 weeks now. Beginning about 10 days ago, I started having a sore throat. It doesn't seem to be getting any better, and in fact it hurts worse the last 2 days. I have a history of allergy/drainage problems, but this only hurts on one side of my throat, and my nose doesn't feel like it's draining. That side of my throat (tonsil area) is very red and swollen. There has been a little bit of puss in the area, but it appears to have gone away today.

Could this be due to the sulfazine, or is it possibly be unrelated?