Background: Non-steroidal anti-inflammatory drugs (NSAIDs) damage the small intestine by causing multiple erosions and ulcers. However, to date, no established therapies and prophylactic agents are available to treat such damages. We reviewed the role of intestinal microbiota in NSAID-induced intestinal damage and identified potential therapeutic candidates. Summary: The composition of the intestinal microbiota is an important factor in the pathophysiology of NSAID-induced small intestinal damage. Once mucosal barrier function is disrupted due to NSAID-induced prostaglandin deficiency and mitochondrial malfunction, lipopolysaccharide from luminal gram-negative bacteria and high mobility group box 1 from the injured epithelial cells activate toll-like receptor 4-signaling pathway and nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 inflammasome; this leads to the release of proinflammatory cytokines such as tumor necrosis factor-α and interleukin-1β. Proton pump inhibitors (PPIs) are often used for the prevention of NSAID-induced injuries to the upper gastrointestinal tract. However, several studies indicate that PPIs may induce dysbiosis, which may exacerbate the NSAID-induced small intestinal damage. Our recent research suggests that probiotics and rebamipide could be used to prevent NSAID-induced small intestinal damage by regulating the intestinal microbiota. Key Messages: Intestinal microbiota plays a key role in NSAID-induced small intestinal damage, and modulating the composition of the intestinal microbiota could be a new therapeutic strategy for treating this damage.

Proton pump inhibitors (PPIs) alter the composition of the intestinal microbiome, exacerbating indomethacin (IND)-induced small intestinal damage. Vonoprazan fumarate inhibits gastric acid secretion using a different mechanism from PPIs. We investigated the effects of both drugs on the intestinal microbiome and IND-induced small intestinal damage. We sought to clarify whether PPI-induced dysbiosis and worsening of the damage were due to a specific drug class effect of PPIs. Rabeprazole administration increased operational taxonomic unit numbers in the small intestines of C57BL/6 J mice, whereas the difference was not significant in the vonoprazan-treated group but exhibited a trend. Permutational multivariate analysis of variance of the unweighted UniFrac distances showed significant differences between vehicle- and vonoprazan- or rabeprazole-treated groups. L. johnsonii was the predominant microbial species, and the population ratio decreased after vonoprazan and rabeprazole administration. The vonoprazan- and rabeprazole-treated groups showed increased IND-induced damage. This high sensitivity to IND-induced damage was evaluated by transplantation with contents from the small intestine of mice treated with either vonoprazan or rabeprazole. Supplementation of L. johnsonii orally in mice treated with rabeprazole and vonoprazan prevented the increase in IND-induced small intestinal damage. In conclusion, both rabeprazole and vonoprazan aggravated NSAID-induced small intestinal injury by reducing the population of L. johnsonii in the small intestine via suppressing gastric acid secretion.

Background: Obscure gastrointestinal bleeding (OGIB) is a common but embarrassing problem for gastroenterologists. Most bleeding lesions associated with OGIB are present in the small intestine and sometimes cannot be identified due to the difficulty associated with physical accessibility. Capsule endoscopy (CE) and double-balloon enteroscopy (DBE) have enabled in the process of diagnosing and have evolved to become approaches to treating OGIB. Summary: CE is a minimally invasive procedure and has a high diagnostic yield in patients with OGIB. DBE offers additional advantage of biopsy collection for pathological diagnosis and therapeutic intervention, but it should be noted that it sometimes causes severe adverse events such as acute pancreatitis, intestinal bleeding, and intestinal perforation. CE should be performed early in the workup course of OGIB. Positive CE findings enhance the diagnostic yield of subsequent DBE, and the effective therapeutic intervention improves the clinical outcomes of OGIB patients. On the contrary, there are no clear guidelines for further investigation of patients with negative CE findings at the present. Although patients in stable general condition may only require follow-up, repeated CE is useful to detect positive findings in patients with evidence of sustained bleeding and progressing anemia. We have revealed that repeated CE has higher positive finding rate than DBE in OGIB patients with negative CE findings in a preliminary study. Key Messages: CE and DBE have complementary roles in the management of OGIB, and the precise timing and proper sequence may be important for the approach to treating OGIB.

There is no effective treatment for aspirin-induced small bowel ulcer bleeding. We performed a double-blind, randomized, placebo-controlled trial to determine whether misoprostol can heal small bowel ulcers in patients with small bowel bleeding who require continuous aspirin therapy. We performed a prospective study of 84 aspirin users with small bowel bleeding who required continued aspirin therapy in Hong Kong and Japan. Patients with small bowel ulcers or multiple erosions, detected by capsule endoscopy, were randomly assigned to groups that received either misoprostol (200 μg, 4 times daily; n = 42) or placebo (n = 42) for 8 weeks. All patients continued taking aspirin (100 mg, once daily). The primary end point was complete ulcer healing at follow-up capsule endoscopy. Secondary end points included changes in hemoglobin level and number of ulcer/erosions from baseline. Complete healing of small bowel ulcers was observed in 12 patients in the misoprostol group (28.6%; 95% confidence interval [CI], 14.9%–42.2%) and 4 patients in the placebo group (9.5%; 95% CI, 0.6%–18.4%), for a difference in proportion of 19.0% (95% CI, 2.8%–35.3%; P = .026). The misoprostol group had a significantly greater mean increase in hemoglobin than the placebo group (mean difference, 0.70 mg/dL; 95% CI, 0.05–1.36; P = .035). The reduction in medium number of ulcers or erosions was significantly greater in the misoprostol group (from 6.5 [range, 1–85] to 2 [range, 0–25]) than in the placebo group (from 7 [range, 1–29] to 4 [range, 0–19] (P = .005). In a double-blind, randomized, placebo-controlled trial, we found misoprostol to be superior to placebo in promoting healing of small bowel ulcers among aspirin users complicated by small bowel ulcer bleeding who require continuous aspirin therapy. However, use of misoprostol alone would provide only limited protection against aspirin on the small bowel. ClinicalTrials.gov ID NCT01998776.