Misoprostol for small bowel ulcers in patients with obscure bleeding taking aspirin and non-steroidal anti-inflammatory drugs (MASTERS): a randomised, double-blind, placebo-controlled, phase 3 trial.

Background: The incidence of obscure gastrointestinal bleeding, which originates from the small bowel and is mainly associated with the use of aspirin and non-steroidal anti-inflammatory drugs (NSAIDs), is rising. We assessed the efficacy and safety of misoprostol for the treatment of small bowel ulcers and erosions in patients taking low-dose aspirin or NSAIDs with obscure gastrointestinal bleeding.

Methods: In this randomised, double-blind, placebo-controlled, phase 3 trial, we recruited patients (aged ≥18 years) with small bowel ulcers who were taking low-dose aspirin, NSAIDs, or both for a minimum of 4 weeks, at University Hospital Crosshouse (Kilmarnock, UK). Eligible patients had evidence of obscure gastrointestinal bleeding (iron deficiency anaemia, a decrease in haemoglobin concentration of ≥20 × 10 mg/L, or positive faecal occult blood test) and normal upper endoscopy and colonoscopy. Patients were randomly assigned (1:1) using an interactive voice response system to receive 200 μg oral misoprostol or placebo four times daily for 8 weeks. Patients, investigators, and assessors were masked to treatment allocation. The primary endpoint was the complete healing of small bowel ulcers and erosions, assessed by video capsule endoscopy after 8 weeks of treatment. Primary analysis was by modified intention to treat, which included all randomised patients who received at least one dose of study treatment. Safety was assessed in the same population. The trial is registered with ClinicalTrials.gov, number NCT02202967.

Findings: Between Jan 7, 2016, and Oct 11, 2017, we randomly allocated 104 eligible patients: 52 to receive misoprostol and 52 to receive placebo. Two patients allocated to misoprostol were later found to meet one of the exclusion criteria, thus 50 randomly assigned patients in the misoprostol group and 52 patients in the placebo group received at least one dose of study treatment. Complete healing of small bowel ulcers and erosions was noted at week 8 in 27 (54%) of 50 patients in the misoprostol group and nine (17%) of 52 patients in the placebo group (percentage difference 36·7%, 95% CI 19·5-53·9; p=0·0002). Adverse events occurred in 23 (46%) of 50 patients in the misoprostol group and 22 (42%) of 52 patients in the placebo group. The most common adverse events were abdominal pain (ten [20%] in the misoprostol group vs 13 [25%] in the placebo group), nausea or vomiting (nine [18%] vs seven [13%]), and diarrhoea (11 [22%] vs six [12%]). Four (8%) of 50 patients in the misoprostol group had severe adverse events, compared with none in the placebo group. No serious adverse events were reported.

Interpretation: Misoprostol is effective for the treatment of small bowel ulcers and erosions in patients using low-dose aspirin and NSAIDs. Misoprostol might represent a pharmacological treatment option for lesions causing obscure gastrointestinal bleeding that is associated with aspirin and NSAIDs, but its use should be balanced against the risk of side-effects.

Funding: National Health Service (NHS) Greater Glasgow and Clyde and NHS Ayrshire and Arran.