葉酸
Patients on high dose sulfasalazine require folic supplementation (1 mg/day) (1000 µg/day) to maintain normal cell division. This may, however, be counter-productive for patients who are also taking methotrexate, which is a folic acid inhibitor. Folic acid might also be counter-productive for patients taking 6-MP and related drugs that inhibit all cell division.