Irritable bowel syndrome, known as IBS, is a functional gastrointestinal disorder characterized by recurrent episodes of abdominal pain or discomfort accompanied by diarrhea, constipation, or both. The term “functional disorder” refers to the fact that symptoms occur in the absence of identifiable anatomic or metabolic disease. In a 2010 report in “Current Opinion in Gastroenterology,” Drs. Hoonmo L. Koo and Herbert L. Dupont explain that rifaximin is an antibiotic that has recently emerged as a drug of interest in the treatment of irritable bowel syndrome.
Therapeutic Rationale
Koo and Dupont report that current evidence implicates bacterial overgrowth within the small intestine as a cause of IBS. According to the American College of Gastroenterology, patients with diarrhea-predominant IBS are most likely to suffer from this problem.
Mechanism of Action
Rifaximin belongs to a class of drugs known as rifamycins that work by inhibiting bacterial protein synthesis in a broad spectrum of bacteria. Rifaximin is poorly absorbed, which means that it achieves high concentrations in the gastrointestinal tract without affecting other systems of the body.
Dosing and Administration
When used to treat IBS, physicians usually prescribe rifaxamin—brand name Xifaxan--as a seven to ten day course of 1200 to 1600 mg per day. Patients take the drug by mouth in three or four divided doses of 400 mg each.
Side Effects
Since rifaximin mostly stays in the gastrointestinal tract, it produces few side effects. Some patients who take rifaximin report vomiting. According to Koo and Dupont, in clinical studies, patients treated with rifaximin experienced comparable or lower rates of adverse events than those treated with placebo or other common antibiotics.
Contraindications
Pregnant women and people with liver disease should not take rifaximin for IBS. People with a history of allergic reactions to related drugs, such as rifabutin—brand name Mycobutin; rifampin—brand names Rifadin, Rifamate, Rifater, Rimactane; and rifapentine--brand name Priftin, should share this information with their health care providers before taking rifaximin.
Effectiveness
According to Koo and Dupont, patients who take rifaximin compared to a placebo report significantly greater improvements in symptoms up to ten weeks after treatment. Many patients, especially those who take other drugs such as proton pump inhibitors, require more than one course of treatment because symptoms eventually come back.
References
- "Current Opinion in Gastroenterology"; Rifaximin: a unique gastrointestinal-selective antibiotic for enteric disease; H.L. Koo and H.L. Dupont; 2010
- American College of Gastroenterology: Understanding Irritable Bowel Syndrome
- MedlinePlus: Rifaximin
