With a lot of prescription drugs being made in China, no real surprise if we're seeing shortages. Hope you can find an alternative.
And yeah there are more shortages
https://www.accessdata.fda.gov/scripts/drugshortages/dsp_ActiveIngredientDetails.cfm?AI=Sulfasalazine+T ablets&st=c&tab=tabs-4&panels=1
Hit "Teva" it shows as available. Maybe a generic?