Rifaximin

Indications

Rifaximin is used for: Traveler's diarrhea, irritable bowel syndrome

Adult Dose

Traveler's Diarrhea 200 mg PO q8hr for 3 days Hepatic Encephalopathy Maintenance of remission 550 mg PO q12hr Irritable Bowel Syndrome Indicated for irritable bowel syndrome with diarrhea (IBS-D) in adult men and women 550 mg PO q8hr for 14 days; recurrence of symptoms can be retreated with a 14 day treatment course, up to 2 times

Child Dose

Traveler's Diarrhea <12 years: Safety and efficacy not established >12 years: 200 mg PO q8hr for 3 days, with or without food

Renal Dose

Administration

May take with or without food

Contra Indications

Contraindicated in patients with a hypersensitivity to Rifaximin or to any of the rifamycin antimicrobial agents, or any components of this product.

Precautions

Rifaximin is not found to be effective in patients with diarrhea complicated by fever and/or blood in the stools. Rifaximin therapy should be discontinued if diarrhea symptoms get worse or persist for more than 24-48 hours and an alternative antibiotic therapy should be considered. Pseudomembranous colitis has been reported with nearly all antibacterial agents and may range in severity from mild to life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of antibacterial agents. Lactation: Do not use if nursing or do not nurse

Pregnancy-Lactation

Pregnancy category: C Lactation: Do not use if nursing or do not nurse

Interactions

Although in vitro studies demonstrated the potential of rifaximin to interact with cytochrome P450 (CYP3A4), a clinical drug-drug interaction study demonstrated that rifaximin did not significantly affect the pharmacokinetics of midazolam. An additional clinical drug-drug interaction study showed no effect of rifaximin on the presystemic metabolism of an oral contraceptive containing ethinyl estradiol and norgestimate. Therefore, clinical interactions with drugs metabolized by human cytochrome P450 isozymes are not expected.

Adverse Effects

Side effects of Rifaximin : >10% Flatulence (11%) 1-10% Headache (10%), Rectal tenesmus (7%), Abdominal pain (7%), Defecation urgency (6%), Nausea (5%), Constipation (4%), Pyrexia (3%), Vomiting (2%) Frequency Not Defined Hypersensitivity reactions (including allergic dermatitis), Pruritus, Rash

Mechanism of Action

Antimicrobial action is a result of binding to the beta-subunit of bacterial DNA-dependent RNA polymerase, resulting in inhibition of transcription. Hepatic encephalopathy: Inhibits growth of enteric ammonia-producing bacteria to indirectly reduce serum ammonia level. Irritable bowel syndrome with diarrhea (off-label): Inhibits growth of enteric bacteria to reduce gas production.