# Drugs for IBD > Drugs for IBD for FMGE Pharmacology: mesalazine by extent, steroids for induction only, thiopurines, anti-TNF therapy and severe-UC rescue. - Canonical URL: https://prepelephant.com/topics/fmge/pharmacology/drugs-for-ibd-fmge - Exam / course: FMGE · Subject: Pharmacology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Drugs for IBD", PrepElephant, https://prepelephant.com/topics/fmge/pharmacology/drugs-for-ibd-fmge ## 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.