Rx Update: March 2005

Rifaximin
Poison Prevention Week

Joan Murhammer, R.Ph., Mary Ross, R.Ph., M.B.A., Kevin Bebout, R.Ph.
Peer Review Status: Internally Reviewed

Rifaximin (Xifaxan^®) is a non-absorbed rifamycin derivative antibiotic, similar in structure to rifampin.  This nonsystemic antibiotic is FDA-approved to treat traveler’s diarrhea caused by noninvasive strains of E. coli. It has also been used to treat hepatic encephalopathy.

Rifaximin is contraindicated in people with hypersensitivity to rifaximin and rifamycin antibacterial agents (e.g., rifampin).  The most common side effects of rifaximin are gastrointestinal related and include flatulence, abdominal pain, nausea/vomiting, constipation, fecal urgency, tenesmus, headache, and fever.  Since rifaximin lacks systemic absorption, there is a reduced likelihood of systemic side effects and drug interactions.

The recommended dose of rifaximin for adults and children (> 12 years old) for traveler’s diarrhea is 200 mg orally three times a day for three days. The dose used for hepatic encephalopathy is 400 mg orally three times a day. Rifaximin can be administered with or without food.  No specific dosage adjustments are recommended for patients with hepatic or renal insufficiency because of the drug’s minimal systemic absorption. Rifaximin is commercially available as 200 mg tablets.

March 20 to 26, 2005, is being observed as National Poison Prevention Week.  According to the American Association of Poison Control Centers (AAPCC) Toxic Exposure Surveillance System, 2.4 million poisonings were reported to poison centers during 2003. The top categories of agents involved in poisoning exposures in order of their frequency were: analgesics, cleaning products, cosmetics, foreign bodies, sedatives/hypnotics/ antipsychotics, topicals, cough and cold preparations, antidepressants, insecticides/pesticides,  bites/ envenomations, plants, antihistamines, alcohols, and food poisoning,   Pharmaceutical exposures have more severe outcomes; 84.7% of fatalities involved pharmaceuticals. The pharmaceutical agents most commonly involved in fatalities in order of frequency were: analgesics, stimulants and street drugs, antidepressants, cardiovascular drugs, and sedatives/hypnotics/antipsychotics.

As health care professionals, there are some simple steps we can take to decrease future fatalities:

• Counsel all patients on the proper use and storage of medications.  A study found that 23% of the oral prescription drugs that were ingested by children under 5 years of age belonged to someone who did not live with the child.
• Encourage family members, friends, and patients to poison-proof their homes.
• If a suspected poisoning occurs, immediately call the poison center (1-800-222-1222).  Not all exposures necessarily result in a poisoning.  The staff of the poison center, through careful history taking, will provide you with the proper management.
• Keep the number of the poison center (1-800-222-1222) readily available.

The Drug Information Center has two informational poison brochures and telephone stickers available upon request by calling 6-2600.

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