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. 2012 May 25;5:69–100. doi: 10.2147/CEG.S29023

Table 2.

Randomized controlled trials of rifaximin in irritable bowel syndrome: study characteristics and efficacy outcomes

Study Diagnostic criteria Sample size, type of IBS,* dosage, analysis population Study type and duration Relief of abdominal pain with or without discomfort Relief of bloating and/or distension Effect on stool frequency Effect on stool consistency Effect on urgency Global or overall IBS improvement Other efficacy assessments
Pimentel et al11 Rome I Patients: 87, aged 18–65 yr, with IBS without an underlying condition predisposing to SIBO, 66% women
Treatment: rifaximin 400 mg tid vs placebo for 10 days in 1:1 ratio in blocks of 4 patients (rifaximin = 43, placebo = 44)		 Randomized, DB, PC design; 10-d treatment. 10 wk follow-up VAS-abdominal pain: 0 VAS-bloating: +, P = 0.010 NA/NR NA/NR NA/NR Overall improvement: +, P = 0.020 VAS-diarrhea:
0, diarrhea common AE
Sharara et al12

  1. Intestinal gas-related symptoms

  2. Rome II

  3. Patient not meeting Rome II

 Patients: 124, 54% men
Treatment: rifaximin 400 mg bid vs placebo
Analysis population:

  1. History of bloating and/or excessive flatulence for >12 wk and any of the following:

    chronic abdominal pain or discomfort, disturbances in bowel movements including feeling of incomplete evacuation, or abnormal stool consistency

  2. 70 IBS patients met

    Rome II criteria with 20% IBS-D, 42% IBS-A, 38% IBS-C

  3. 54 patients did not meet Rome II criteria

 Randomized, DB, PC design; 10 d treatment, 10 d follow-up NA/NR

  1. +, P = 0.02

  2. NA/NR

 NA/NR NA/NR NA/NR Subjective feeling of symptom relief at end of treatment:

  1. +, P = 0.03

  2. +, P = 0.04

  3. 0;

Subjective feeling of symptom relief at end of follow-up:

  1. +, P = 0.02

  2. +, P = 0.05

 1. Mean symptom score at end of treatment: +, P = 0.03;
At follow-up: 0
IBS-D phase II study

  1. Lembo et al13

  2. Ringel et al14

  3. Pimentel et al15

  4. Chey et al16

 Rome II Patients: 388 with IBS-D
Treatment: rifaximin 550 mg bid for 14 d vs placebo		 DB, multicenter design; 14 d DB treatment, 14 d placebo, followed by 12 wk follow-up

  1. NA/NR

  2. NA/NR

  3. NA/NR

  4. NA/NR

  1. Adequate relief of IBS-related bloating symptoms:

    At end of treatment: +, P = 0.04; At end of follow-up: +, P < 0.05

  2. and/or

  3. In patients with baseline abdominal pain mild-moderate:

    0 or severe: 0; Relief of bloating symptoms in patients with baseline bloating mild to moderate: +, P = 0.03, or severe: 0.

  4. NA/NR

  1. NA/NR

  2. NA/NR

  3. NA/NR

  4. NA/NR

  1. NA/NR

  2. NA/NR

  3. NA/NR

  4. NA/NR

  1. NA/NR

  2. NA/NR

  3. NA/NR

  4. NA/NR

  1. Adequate relief of global symptoms:

    At end of treatment: +, P = 0.03; At end of follow-up: +, P < 0.05

  2. and/or

  3. Relief of global symptoms in patients with baseline abdominal pain mild-moderate: +, P = 0.04, and severe: 0; Relief of global symptoms in patients with baseline bloating mild to moderate: +, P = 0.006, and severe: 0

  4. NA/NR

  1. NA/NR

  2. and/or

  3. The most substantial confounders of clinical response were daily bloating, abdominal pain, and use of rescue medications

  4. IBS-QOL total score: +, P = 0.02; also +, P < 0.05 for dysphoria, body image, health worry, social reaction, and relationship improvements
Pimentel et al17
TARGET 1 and TARGET 2 studies17 		Rome II Patients: 1260 with nonconstipated IBS enrolled in 2 identically designed TARGET 1 (n = 623) and TARGET 2 (n = 637) studies
Treatment: rifaximin 550 mg tid vs placebo:

  1. TARGET 1

  2. TARGET 2

  3. Total from both trials

 Randomized, DB, PC, PG design; 2 wk treatment, 10 wk follow-up Daily abdominal pain improvement (for at least 2 of first 4 wk after treatment):

  1. +, P = 0.02

  2. +, P = 0.02

  3. +, P < 0.001

 Defined as for at least 2 of first 4 wk after treatment (weekly assessment):

  1. +, P = 0.005

  2. +, P = 0.02

  3. +, P < 0.001

 NA/NR Daily symptoms

  1. +, P < 0.001

  2. +, P = 0.01

  3. +, P < 0.001

 NA/NR Defined as relief for at least 2 of first 4 wk after treatment (weekly assessment):

  1. +, P = 0.01

  2. +, P = 0.03

  3. +, P < 0.001

 Relief of IBS-related abdominal pain and loose or watery stools for at least 2 of first 4 wk after treatment based on daily assessments:

  1. +, P = 0.04

  2. +, P = 0.008

  3. +, P < 0.001

Notes:

*

According to predominant stool pattern, if available. + Indicates significant improvement over placebo; 0 represents no statistically significant difference between active treatment and placebo. If a study did not report on a particular assessment, it was noted as “not assessed.” If more than one population is assessed for a particular parameter, the populations are numbered (see sample size, type of IBS, dosage, analysis population column); subsequent efficacy values are presented to correspond to the population so designated.

Abbreviations: AE, adverse event; DB, double-blind; 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; NA/NR, not assessed or not reported; PC, placebo-controlled; PG, parallel group; SIBO, small intestinal bowel overgrowth; VAS, visual analog scale.