Concomitant irritable bowel syndrome does not influence the response to antimicrobial therapy in patients with functional dyspepsia

Background and Aims: Antimicrobial therapy improves symptoms in patients with irritable bowel syndrome (IBS), but the efficacy in functional dyspepsia (FD) is largely unknown. While FD and IBS frequently overlap, it is unknown if concomitant IBS in FD alters the response to antimicrobial therapy in FD. Thus, we aimed to assess and compare the effect of antimicrobial therapy on visceral sensory function and symptom improvement in FD patients with and without IBS. Methods: Adult patients with FD with or without IBS received rifaximin 550 mg BD for 10 days, followed by a 6-week follow-up period. The total gastrointestinal symptom score as measured by the SAGIS (Structured Assessment of Gastrointestinal Symptoms) questionnaire and subscores (dyspepsia, diarrhea, and constipation), symptom response to a standardized nutrient challenge and normalization of the glucose breath tests were measured. Results: Twenty-one consecutive adult patients with FD and 14/21 with concomitant IBS were recruited. Treatment with rifaximin resulted in a significant (p = 0.017) improvement in the total SAGIS score from 34.7 (± 15.4) at baseline to 26.0 (± 16.8) at 2 weeks and 25.6 (± 17.8) at 6 weeks post-treatment. Similarly, compared to baseline there was a statistically significant improvement in SAGIS subscores for dyspepsia and diarrhea (all p < 0.05) and effects persisted for 6 weeks post-treatment. Similarly, the symptom score (and subscores) following a standardized nutrient challenge improved significantly (p < 0.001) 2 weeks post-treatment. The presence of concomitant IBS did not significantly influence the improvement of symptoms after antibiotic therapy (all p > 0.5). Conclusions: In FD patients, the response to antimicrobial therapy with rifaximin is not influenced by concomitant IBS symptoms.