Can a patient with Inflammatory Bowel Disease (IBD) continue Azathioprine following a gastrostomy insertion and formation of a split ileostomy?

Azathioprine Continuation Following Gastrostomy and Split Ileostomy in IBD

Yes, patients with IBD can safely continue azathioprine therapy following gastrostomy insertion and formation of a split ileostomy. 1 Azathioprine remains an important immunomodulator for maintaining disease control in IBD patients who have undergone surgical interventions.

Evidence-Based Rationale

Azathioprine in Post-Surgical IBD Management

Azathioprine (1.5–2.5 mg/kg/day) is recommended as a first-line agent for steroid-dependent IBD disease 1. The guidelines make no distinction regarding surgical status when recommending immunomodulator therapy, focusing instead on disease activity and steroid dependence as the primary considerations.

Current practice positions specifically state that:

• Immunomodulators, including azathioprine, can be continued during the peri-operative period 1
• Evidence suggests that purine analogues (azathioprine and mercaptopurine) do not adversely affect postoperative outcomes 1

Pharmacological Considerations

Several important pharmacological factors support continuing azathioprine:

1. Washout Period: Thiopurines can take up to 3 months to reach therapeutic levels and require approximately 3 months to fully wash out of the system 1
2. Immediate Restart: Azathioprine has an elimination half-life of 1-2 hours and can be safely restarted while recommencing oral intake in the immediate postoperative period 1
3. Absorption: Despite the altered GI anatomy with a gastrostomy and ileostomy, azathioprine absorption should remain adequate as it is primarily absorbed in the upper GI tract

Monitoring Requirements

When continuing azathioprine, appropriate monitoring should include:

• Full blood count within 4 weeks of starting therapy and every 6–12 weeks thereafter 1
• Liver function tests at regular intervals
• Monitoring for clinical signs of myelosuppression, which can develop rapidly despite monitoring 1

Special Considerations for Patients with Stomas

For patients with a split ileostomy:

• The presence of an ileostomy does not contraindicate azathioprine use
• Monitoring for dehydration and electrolyte abnormalities is important, as high-output stomas can affect medication absorption and increase risk of adverse effects
• Dose adjustments may be necessary based on clinical response and drug levels if available

Clinical Efficacy in IBD

Azathioprine has demonstrated efficacy in:

• Maintaining clinical remission rates of 75% in patients who complete six months of treatment 2
• Providing steroid-sparing effects in steroid-dependent disease 1, 3
• Maintaining remission at 12 months in 87.5% of patients 2

Potential Risks and Adverse Effects

Be aware of potential side effects that may require monitoring:

• Adverse events occur in approximately 33.3% of patients, requiring discontinuation in 13.3% 2
• Most dose-dependent adverse events occur between 12-18 months after starting treatment 4
• Common side effects include myelosuppression, hepatotoxicity, pancreatitis, and increased risk of infections 5

Conclusion for Clinical Practice

When managing a patient with IBD who has undergone gastrostomy insertion and split ileostomy formation:

1. Continue azathioprine at the established effective dose (typically 1.5-2.5 mg/kg/day)
2. Maintain regular blood monitoring (CBC every 6-12 weeks)
3. Assess for signs of drug toxicity or reduced efficacy
4. Consider therapeutic drug monitoring if available to ensure adequate drug levels despite altered GI anatomy
5. Ensure multidisciplinary management between gastroenterology and surgical teams

This approach prioritizes maintaining disease control while minimizing the risk of disease flare that could compromise surgical outcomes and patient quality of life.