What is the initial treatment for inflammatory bowel disease (IBD)?

Initial Treatment for Inflammatory Bowel Disease

For mild to moderate IBD, start with high-dose mesalamine (4 g/daily for Crohn's disease or 2.4-4.8 g/daily for ulcerative colitis), escalating to oral corticosteroids (prednisolone 40 mg daily) for moderate to severe disease or mesalamine failure, and reserve intravenous steroids (hydrocortisone 400 mg/day or methylprednisolone 60 mg/day) for severe disease. 1, 2

Treatment Algorithm by Disease Severity

Mild Disease

• High-dose oral mesalamine is first-line therapy: 4 g/daily for mild ileocolonic Crohn's disease or 2.4-4.8 g/daily for mild to moderate ulcerative colitis 1, 2, 3
• For distal ulcerative colitis, add topical mesalamine to oral therapy to improve remission rates 2, 4
• Topical mesalamine alone may be effective for left-sided colonic disease of mild to moderate activity 1, 2

Moderate to Severe Disease

• Oral prednisolone 40 mg daily is appropriate for patients with moderate to severe disease or those failing mesalamine therapy 1, 2
• Taper prednisolone gradually over 8 weeks according to severity and patient response—more rapid reduction is associated with early relapse 1, 2
• For isolated ileo-caecal Crohn's disease with moderate activity, budesonide 9 mg daily is an alternative, though marginally less effective than prednisolone 1

Severe or Fulminant Disease

• Intravenous steroids are required: hydrocortisone 400 mg/day or methylprednisolone 60 mg/day 1, 2
• Concomitant intravenous metronidazole is often advisable, as it may be difficult to distinguish between active disease and septic complications 1
• Severe ulcerative colitis should be managed jointly by gastroenterology and colorectal surgery, with patients informed of a 25-30% chance of needing colectomy 1

Disease-Specific Considerations

Crohn's Disease Location and Pattern

• Assess site (ileal, ileocolic, colonic), pattern (inflammatory, stricturing, fistulating), and activity before treatment decisions 1
• Sulphasalazine 4 g daily is effective for active colonic Crohn's disease but not recommended as first-line therapy due to high incidence of side effects 1
• Metronidazole 10-20 mg/kg/day, though effective, is not first-line therapy but has a role in colonic or treatment-resistant disease 1

Fistulating and Perianal Crohn's Disease

• Metronidazole 400 mg three times daily and/or ciprofloxacin 500 mg twice daily are first-line treatments for simple perianal fistulae 1
• Define anatomy with MRI and examination under anesthesia for complex fistulating disease 1

Adjunctive and Steroid-Sparing Therapies

Immunomodulators

• Azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day may be used as adjunctive therapy and steroid-sparing agents, though slow onset of action precludes use as sole therapy 1, 2

Nutritional Therapy

• Elemental or polymeric diets are less effective than corticosteroids but may be used in selected patients with contraindications to corticosteroids or who prefer to avoid such therapy 1, 2
• Total parenteral nutrition is appropriate adjunctive therapy in complex, fistulating disease 1

Biologic Therapy

• Infliximab 5 mg/kg is effective for moderate-severe disease failing conventional therapy, but should be avoided in patients with obstructive symptoms 1, 2, 5
• For fistulizing Crohn's disease, infliximab (three infusions of 5 mg/kg at 0,2, and 6 weeks) should be reserved for refractory cases and used as part of a strategy including immunomodulation and surgery 1

Maintenance Therapy

• Patients with ulcerative colitis should normally receive maintenance therapy with aminosalicylates, azathioprine, or mercaptopurine to reduce risk of relapse 1, 2
• Maintenance therapy is especially important for patients with left-sided or extensive disease, and those with distal disease who relapse more than once a year 1, 2
• For Crohn's disease, smoking cessation is probably the most important factor in maintaining remission 1

Critical Pitfalls to Avoid

• Do not use antidiarrheal medications in active colitis—they can mask worsening symptoms while allowing inflammation to progress and may predispose to toxic dilatation 4
• Rule out infectious causes (C. difficile, other pathogens) before initiating immunosuppressive therapy 6
• Discontinue NSAIDs when possible, as they are associated with increased incidence of colitis 6
• Monitor renal function periodically in patients on mesalamine, particularly those with existing renal disease or taking nephrotoxic drugs 3
• Surgery should be considered for those who have failed medical therapy and may be appropriate as primary therapy in patients with limited ileal or ileo-caecal Crohn's disease 1