Drugs for IBD
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Direct answer
Anatomic extent dictates the first prescription in inflammatory bowel disease. Ulcerative colitis confined to the rectum gets topical mesalazine suppositories; left-sided disease adds oral mesalazine 2–4 g daily with enemas; extensive colitis and Crohn's ileocolitis escalate through induction prednisolone 40 mg daily (never as maintenance), then steroid-sparing azathioprine 2–2.5 mg/kg, then biologics — infliximab 5 mg/kg at weeks 0, 2 and 6, adalimumab, the gut-selective anti-integrin vedolizumab or the IL-12/23 blocker ustekinumab. Mesalazine has a weak role in Crohn's disease, which is treated by steroids, immunomodulators and biologics. Acute severe ulcerative colitis is an admission: intravenous hydrocortisone, with infliximab or intravenous ciclosporin 2 mg/kg as rescue before colectomy. Thiopurine-plus-anti-TNF combination carries a small but specific lymphoma risk that must be weighed, not ignored.
What you must remember
- Extent-matched mesalazine: proctitis — suppository 1 g daily; left-sided — oral plus enema; extensive UC — oral 2.4–4.8 g daily; topical therapy outperforms oral for distal disease.
- Steroids induce remission only: prednisolone 40 mg tapered over 8–12 weeks; any patient needing repeated steroids earns a steroid-sparing drug — azathioprine, 6-mercaptopurine or methotrexate (the latter for Crohn's, not colitis).
- Azathioprine: 2–2.5 mg/kg daily; check TPMT; onset of benefit takes 8–12 weeks; monitor CBC for leukopenia; the combination with allopurinol is dangerous.
- Infliximab: 5 mg/kg IV at 0, 2 and 6 weeks, then every 8 weeks; combine with azathioprine to prevent anti-drug antibodies (the SONIC principle); screen for TB and hepatitis B first.
- Vedolizumab is gut-selective (anti-α4β7 integrin) with low systemic infection risk — chosen in elderly or infected patients; natalizumab, its non-selective sibling, carries progressive multifocal leukoencephalopathy risk.
- Smoking paradox: smoking worsens Crohn's and is (epidemiologically) protective in ulcerative colitis — cessation is Crohn's therapy.
- Severe UC rescue ladder: IV hydrocortisone 100 mg four times daily; if no improvement by day 3, rescue with infliximab or ciclosporin 2 mg/kg; failing that, colectomy — check Clostridioides difficile stool toxin daily.
- Live vaccines are contraindicated once significant immunosuppression begins; immunise before starting, a viva staple in Indian transplant and IBD clinics alike.
A ward pathway for acute severe colitis
Admit a 24-year-old with six weeks of bloody diarrhoea now passing stools a dozen times nightly. Day one defines severity: pulse above 90, temperature, CRP raised, albumin low, dilated colon on radiograph. Start intravenous hydrocortisone 100 mg four times daily, fluids, thromboprophylaxis with low-molecular-weight heparin (IBD is prothrombotic — an under-asked fact), and send stool for culture and C. difficile toxin. Day three is decision day: more than eight stools, persistent bleeding or a worsening CRP predicts steroid failure — call for rescue, infliximab 5 mg/kg or ciclosporin 2 mg/kg, and involve surgery the same day, because the colectomy window closes with perforation.
If rescue works, build the maintenance bridge: oral prednisolone taper to azathioprine, or continue infliximab every eight weeks with thiopurine cover. Months later, a perianal fistula in a Crohn's patient changes the biologic of choice to infliximab — the agent with the best fistula evidence. Each junction of this pathway (rescue drug timing, the heparin detail, the fistula preference) is the exact currency of NBE clinical stems.
Where students slip
Mesalazine is over-prescribed in exam answers: for Crohn's disease its efficacy is marginal, so a Crohn's stem asking for the maintenance option wants azathioprine, methotrexate or a biologic, not 5-ASA. The second slip is steroid misuse — maintenance steroids are never the answer, and the phrase "repeated courses of prednisolone" in a stem is the cue for steroid-sparing therapy. Third, biologics and infection: any anti-TNF stem with fever or a chest shadow signals tuberculosis or HBV reactivation; screen before starting. Finally, the young male on thiopurine plus anti-TNF with hepatosplenic disease asks about hepatosplenic T-cell lymphoma — rare, but the pairing is textbook-famous and FMGE has tested the combination-risk concept.
Frequently asked questions
Which formulation treats ulcerative proctitis best?
Mesalazine suppositories 1 g daily deliver drug directly to the rectum and outperform oral therapy for distal disease, with enemas reaching the sigmoid.
What is the rescue therapy in steroid-refractory severe UC?
Infliximab 5 mg/kg or intravenous ciclosporin 2 mg/kg; failure of rescue progresses to colectomy, so surgery is involved from day three.
Why is azathioprine combined with infliximab?
Immunogenicity — concomitant thiopurine reduces anti-infliximab antibodies and improves durability, per the SONIC trial, at the cost of a small lymphoma risk.
Is mesalazine effective in Crohn's disease?
Only marginally; Crohn's maintenance relies on thiopurines, methotrexate or biologics, with mesalazine reserved for mild ileal disease at most.
Which IBD biologic is gut-selective?
Vedolizumab, an anti-α4β7 integrin antibody that blocks gut lymphocyte homing without systemic immunosuppression.