Final answer:
Sulfasalazine inhibits bacterial folic acid synthesis, which limits nucleic acid production essential for bacteria and is used mainly for rheumatoid arthritis and ulcerative colitis. Allergic reactions are common toxicities, along with potential megaloblastic anemia and G.I. issues.
Step-by-step explanation:
The mechanism of action of sulfasalazine involves its function as a structural analog of para-aminobenzoic acid (PABA). Sulfasalazine and its metabolites inhibit the bacterial enzyme dihydropteroate synthase, blocking the conversion of PABA into dihydrofolic acid and subsequently interfering with folic acid synthesis. This results in a reduced production of nucleic acids, essential for bacterial growth, providing a bacteriostatic effect against a variety of gram-positive and gram-negative bacteria. Clinically, sulfasalazine is used primarily in the treatment of rheumatoid arthritis and ulcerative colitis. It may also be part of the therapeutic regimen for Crohn's disease and ankylosing spondylitis. Toxicities associated with sulfasalazine include allergic reactions, which are relatively common owing to its sulfa component. Other potential side effects include megaloblastic anemia, leukopenia, and G.I. tract disturbances due to interference with the microbial synthesis of folic acid, which impacts cell division and DNA synthesis. When treating patients with sulfa allergies, care must be taken to distinguish between sulfonamides and other sulfur-containing compounds like sulfates and sulfites, as they do not share the same hypersensitivity reactions characteristic of sulfonamides.