Table 3.
Characteristics of randomized controlled trials of nonabsorbable antibiotics in IBS and efficacy outcomes
| Study | Treatment | Study duration | N | Population | Relief of abdominal pain | Relief of bloating | Global/overall IBS improvement | Stool frequency | Stool consistency | Urgency | Other efficacy assessments |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Neomycin vs placebo | |||||||||||
| Pimentel et al21 | 500 mg bid | 10 d treatment, 7 d follow-up | 111 | Adults with IBS (Rome I) | NA/NR | NA/NR | NA/NR | NA/NR | NA/NR | NA/NR | CS:† + for reduction of CS and ≥50% improvement in CS |
| Rifaximin vs placebo | |||||||||||
| Pimentel et al44 | 400 mg tid | 10 d treatment, 10 wk follow-up | 87 | Adults with IBS without underlying predisposition to SIBO (Rome I) | 0 | ++ | + | NA/NR | NA/NR | NA/NR | 0 for diarrhea |
| Sharara et al51 | 400 mg bid | 10 d treatment, 10 d follow-up | 124 | Men with bloating/ flatulence and abdominal discomfort or bowel disturbance or abnormal stool consistency | |||||||
| All patients | NA/NR | + | + for symptom relief at end of treatment; + at end of follow-up | NA/NR | NA/NR | NA/NR | + for mean symptom score at end of treatment; 0 for mean symptom score at end of follow-up | ||||
| 70 with IBS-D, -A, or -C (Rome II) | NA/NR | NA/NR | + for symptom relief at end of treatment; + at end of follow-up | NA/NR | NA/NR | NA/NR | |||||
| 54 who did not meet Rome II criteria | NA/NR | NA/NR | 0 for symptom relief at end of treatment | NA/NR | NA/NR | NA/NR | NA/NR | ||||
| IBS-D phase II study:* Lembo et al54 | 550 mg bid | 14 d treatment, 12 wk follow-up | 388 | Adults with IBS-D (Rome II) | NA/NR | + at end of treatment; + at end of follow-up | + at end of treatment; + at end of follow-up | NA/NR | NA/NR | NA/NR | NA/NR |
| IBS-D phase II study:* Ringel et al55 | 550 mg bid | 14 d treatment, 12 wk follow-up | 388 | Adults with IBS-D (Rome II) | NA/NR | 0 in patients with mild–moderate pain at baseline; 0 in patients with severe pain; + in patients with mild–moderate bloating at baseline; 0 in patients with severe bloating | + in patients with mild–moderate pain at baseline; 0 in patients with severe pain; ++ in patients with mild–moderate bloating at baseline; 0 in patients with severe bloating | NA/NR | NA/NR | NA/NR | Most substantial confounders of clinical response: daily bloating, abdominal pain, and use of rescue medications |
| IBS-D phase II study:* Pimentel et al56 | 550 mg bid | 14 d treatment, 12 wk follow-up | 388 | Adults with IBS-D (Rome II) | NA/NR | 0 in patients with mild–moderate pain at baseline; 0 in patients with severe pain; + in patients with mild–moderate bloating at baseline; 0 in patients with severe bloating | + in patients with mild–moderate pain at baseline; 0 in patients with severe pain; ++ in patients with mild–moderate bloating at baseline; 0 in patients with severe bloating | NA/NR | NA/NR | NA/NR | Most substantial confounders of clinical response: daily bloating, abdominal pain, and use of rescue medications |
| IBS-D phase II study:* Chey et al57 | 550 mg bid | 14 d treatment, 12 wk follow-up | 388 | Adults with IBS-D (Rome II) | NA/NR | NA/NR | NA/NR | NA/NR | NA/NR | NA/NR | + for IBS-QOL total score; + for dysphoria, body image, health worry, social reaction, and relationship improvements |
| TARGET 1 and 2 studies; Pimentel et al58 | 550 mg tid | 2 wk | 1260 | Adults with nonconstipated IBS | |||||||
| 623 in TARGET 1 | + | ++ | ++ | NA/NR | ++ | NA/NR | + for relief during all 3 mo; | ||||
| 637 in TARGET 2 | + | + | + | NA/NR | ++ | NA/NR | ++ for relief during all 3 mo; | ||||
| 1260 in total | ++ | +++ | +++ | NA/NR | +++ | NA/NR | +++ for relief during all 3 mo | ||||
Notes:
Reanalysis of the data from one phase II study.
Composite score based on abdominal pain, diarrhea, and constipation (0–5 scale for each); higher scores denote more severity.
Positive signs indicate significant improvement over placebo: + for P ≤ 0.05; ++ for P ≤ 0.01; +++ for P ≤ 0.001; ++++ for P ≤ 0.0001; 0 represents no statistically significant difference between active treatment and placebo.
Abbreviations: CS, composite score; IBS, irritable bowel syndrome; IBS-A, irritable bowel syndrome with alternating diarrhea and constipation symptom predominance; IBS-C, constipation-predominant IBS; IBS-D, diarrhea-predominant IBS; IBS-QOL, Irritable Bowel Syndrome Quality of Life Questionnaire; SIBO, small intestinal bowel overgrowth.