Aminosalicylates, budesonide and gut-selective biologics in IBD
How sulfasalazine and mesalazine formulations deliver 5-ASA to the right segment of bowel, why first-pass metabolism makes budesonide gut-selective, how vedolizumab's alpha-4-beta-7 target avoids PML, and the IL-12/23 and IL-23 biologics, with the toxicity and interaction questions Paper 1 asks.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Aminosalicylates (5-ASA) act topically on colonic mucosa. Formulation decides where the drug is released, and it matters more than the molecule.
- Budesonide is a potent glucocorticoid with about 90% hepatic first-pass inactivation by CYP3A4, so it treats ileal or colonic mucosa with little systemic exposure.
- Vedolizumab is gut-selective because its target, the alpha-4-beta-7 integrin, binds an addressin found mainly on gut endothelium.
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Sources
- Therapeutic Guidelines: GastrointestinalAU/NZTherapeutic Guidelines Limited, current eTG edition
- Pharmaceutical Benefits Scheme: authority restrictions for biological and small-molecule therapies in Crohn's disease and ulcerative colitisAU/NZAustralian Government Department of Health, Disability and Ageing
- ECCO Guidelines on Therapeutics in Ulcerative Colitis: Medical TreatmentGisbert JP et al., J Crohns Colitis 2026;20(7):jjag066, 2026
- ECCO Guidelines on Therapeutics in Crohn's Disease: Medical TreatmentGordon et al., J Crohns Colitis 2024;18:1531-55, 2024
- Vedolizumab versus adalimumab for moderate-to-severe ulcerative colitis (VARSITY)Sands et al., N Engl J Med 2019;381:1215-26, 2019
- Risankizumab versus ustekinumab for moderate-to-severe Crohn's disease (SEQUENCE)Peyrin-Biroulet et al., N Engl J Med 2024;391:213-23, 2024
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- 14 November 2026
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