Diminished efficacy of colonic adaptation to lactulose occurs in patients with inflammatory bowel disease in remission.

Lactulose has been proposed to be beneficial in treating inflammatory bowel disease (IBD). The hypothesis is based on the prebiotic potential of lactulose. A practical approach to testing its usefulness is to determine colonic adaptation to tolerable doses in patients with IBD. Our objective was to determine if a 3-week course of lactulose will decrease BH2 and symptoms in response to an acute lactulose challenge test in control subjects and IBD patients. The design was a prospective cohort study. Subjects were given a 30-g lactulose challenge test (test 1), and then ingested 10 g of lactulose twice a day for 3 weeks before being retested (Test 2). A third test was given after a further 5-week washout period. The main outcomes were the change in 4-hr sum of BH2 (sum(4HrBH2)) values obtained every 30 min, peak BH2, and 4-hr sum of symptom score (sum(4HrSS)) during the lactulose challenge test. In addition, we also report the change in self-reported symptoms and diarrhea during the 3-week administration of lactulose. In controls, sum(4HrBH2) decreased from test 1 (380.5 +/- 56.6 ppm) to test 2 (288.6 +/- 57.4 ppm) (P < 0.05), and returned toward test 1 levels by test 3 (307.5 +/- 53.1, P > 0.5). Unlike controls, the sum(4HrBH2) in patients failed to achieve significance between test 1 (444.5 +/- 55.8 ppm), test 2 (366.5 +/- 80.7 ppm, P > 0.2) or test 3 (411.6 +/- 62.5 ppm, P > 0.2). Sum(4HrSS) results in controls followed a pattern similar to sum(4HrBH2), achieving significance only in test 2 (P < 0.02). Symptoms during the intertest periods decreased by the third week in controls (P < 0.05), but not in patients (P > 0.5). Symptoms were lower in patients and varied insignificantly both in challenges and intertest periods. In conclusion, although controls adapt to a 3-week period of lactulose ingestion, IBD patients fail to meet the criteria for adaptation. However, longer studies may be needed to establish whether IBD patients are slower to adapt.