Sulfapyridine is not prescribed for treatment in humans any more. However, it may be used to treat Linear IgA Disease. It is a good antibacterial drug, but its water solubility is very pH dependent. Thus there is a risk of crystallization within the bladder or urethra, which could lead to pain or blockage. The drug sulfasalazine is structurally one molecule of mesalamine linked to one molecule of Sulfapyridine with an azo bond.