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Medical Author:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Medical Author:

Bhupinder Anand, MD

In this Article

• What is giardiasis?
• Who is at risk for giardiasis?
• What signs and symptoms does giardiasis cause?
• How is giardiasis diagnosed?
• How is giardiasis treated?
• How can giardiasis be prevented?
• Patient Comments: Giardia Lamblia - Describe Your Experience
• Patient Comments: Giardia Lamblia - Treatments
• Find a local Gastroenterologist in your town
• Giardia Lamblia Index

The most common treatment for giardiasis is metronidazole (Flagyl) for 5-10 days. It eradicates the Giardia more than 85% of the time, but it often causes gastrointestinal side effects such as nausea and a metallic taste as well as dizziness and headache. Despite its effectiveness, metronidazole is not approved by the FDA in the U.S. for treatment of giardiasis.

The only drug approved for treating giardiasis in the U.S. is furazolidone (Furoxone) for 7-10 days. It is approximately as effective as metronidazole. Tinidazole is available outside the U.S. and is highly effective at treating giardiasis(>90%). It also can be given as a single dose and is well tolerated. Quinacrine is very effective for treating giardiasis but is no longer available in the U.S. Paromomycin and albendazole are less effective than other treatments.

Occasionally, treatment fails to eradicate Giardia. In such cases, the drug may be changed or a longer duration or higher dose may be used. Combination therapy also may be effective (e.g., quinacrine and metronidazole).

• Drink only water that has been treated in established treatment facilities.
  
  
• If there is any doubt about the adequacy of the treatment of water, boil the water or filter it through a filter with a pore size of <1 micrometer, which will exclude trophozoites and cysts.
  
  
• Do not drink from fresh water streams or lakes without boiling or filtering the water.
  
  
• Do not use ice or drink beverages made from tap water that may be contaminated.
  
  
• Do not brush teeth with tap water that may be contaminated.
  
  
• Do not eat uncooked or unpeeled fruits or vegetables grown in conditions in which contamination with Giardia might occur.
  
  
• Wash hands before eating food, after changing diapers, using the bathroom, or touching pets.
  
  
• Avoid oral/anal sex.

REFERENCE: eMedicine.com. Giardiasis.
<http://emedicine.medscape.com/article/176718-overview>

Previous contributing editor Dennis Lee, MD