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Giardiasis (cont.)

Giardiasis Medications and Treatment

Medications are used effectively to treat giardiasis.

Metronidazole (Flagyl)

  • This is the most common and most often recommended drug to treat giardiasis.
  • Treatment is highly effective with these pills, given 3 times a day for 5 days.
  • SSide effects may include nausea, vomiting, headache, dry mouth, or a metallic taste in the mouth. Urine may turn dark or reddish-brown. Metronidazole brings on nausea and vomiting when alcohol is consumed while on the medication. Avoid alcohol 24 hours before starting the drug and for 48 hours after the last dose.


  • Treatment is highly effective with these pills, given over 5 days. Side effects may include nausea, vomiting, yellow skin and eyes, dark urine, and a rash.

Nitazoxanide (Alinia)

  • Nitazoxanide is available in liquid form and must be taken with food. Side effects may include stomach pain, diarrhea, vomiting, or headache.

Pregnant women with giardiasis are treated somewhat differently because of the possible risk to the fetus by some of the medications.

  • If the disease is mild and dehydration can be avoided, treatment may be postponed until after delivery.
  • If treatment is necessary, paromomycin may be used but is less effective. The effects of metronidazole on the fetus appear to be minimal and occur mostly in the first trimester.
  • If therapy is necessary, metronidazole is probably safe to use in the second and third trimesters.
Medically Reviewed by a Doctor on 12/15/2014
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Giardiasis »

Giardia lamblia was originally identified by von Leeuwenhoek in the 1600s and was first recognized in human stool byVilem Dusan Lambl (1824-1895) in 1859and by Alfred Giard (1846-1908) after whom it is named.

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