Sulfasalazine is prescribed for a patient with mild-to-moderate ulcerative colitis. Which statement about its pharmacology is correct?

• A Sulfapyridine is the therapeutically active moiety acting on the colonic mucosa
• B 5-Aminosalicylic acid serves only as a carrier molecule and has no anti-inflammatory action
• C The intact molecule is absorbed in the jejunum and acts systemically on inflamed mucosa
• D Colonic bacterial azoreduction splits the drug into sulfapyridine and 5-aminosalicylic acid, the latter being the active moiety ✓

Explanation

Sulfasalazine reaches the colon unchanged, where bacterial azoreductases cleave the azo bond, releasing 5-ASA (mesalamine), the active anti-inflammatory compound, and sulfapyridine, the carrier responsible for most adverse effects such as rash, haemolysis and reversible oligozoospermia. Option A reverses the roles of the two moieties, and option B reverses the roles again in the opposite direction.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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