An experiment to determine the active therapeutic moiety of sulphasalazine

Lancet. 1977 Oct 29;2(8044):892-5. doi: 10.1016/s0140-6736(77)90831-5.


Sulphasalazine (S.A.S.P.) is of proven value in the treatment of ulcerative colitis, but its mode of action is unknown. When it is taken by mouth, nearly all the dose reaches the colon intact, where it is split by bacteria into sulphapyridine (S.P.) and 5-aminosalicylic acid (5-A.S.A.). An experiment was devised to determine whether the therapeutic property of S.A.S.P. is a function of the parent molecule or of these two principal metabolites. Retention enemas of S.A.S.P., S.P., and 5-A.S.A. were administered to volunteer patients with sigmoidoscopic evidence of active ulcerative colitis. The experiment was conducted as a blind controlled therapeutic trial, each patient having one of the test enemas daily for two weeks. Pronounced histological improvement was observed in approximately 30% of the patients receiving S.A.S.P. or 5-A.S.A., and in only 5% of those receiving S.P. It is concluded that the active therapeutic moiety of S.A.S.P. IS 5-A.S.A. and that the S.P. functions as a carrier ensuring that the 5-A.S.A. is liberated within the colon.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Topical
  • Aminosalicylic Acids / administration & dosage
  • Aminosalicylic Acids / pharmacology
  • Aminosalicylic Acids / therapeutic use
  • Clinical Trials as Topic
  • Colitis, Ulcerative / drug therapy*
  • Double-Blind Method
  • Drug Evaluation
  • Enema
  • Follow-Up Studies
  • Humans
  • Sulfapyridine / administration & dosage
  • Sulfapyridine / pharmacology
  • Sulfasalazine / administration & dosage
  • Sulfasalazine / pharmacology
  • Sulfasalazine / therapeutic use*


  • Aminosalicylic Acids
  • Sulfasalazine
  • Sulfapyridine