Treatment of giardiasis

Drug	Dose
Drug	Adults	Children
Drugs of choice
Tinidazole*	2 g orally, single dose^¶	Age ≥3 years: 50 mg/kg orally, single dose (maximum dose 2 g)
Nitazoxanide^Δ	500 mg orally 2 times per day for 3 days	Age 1 to 3 years: 100 mg orally 2 times per day for 3 days Age 4 to 11 years: 200 mg orally 2 times per day for 3 days Age ≥12 years: Same as adult dose
Alternative agents
Metronidazole^◊	500 mg orally twice daily OR 250 mg orally 3 times per day; duration 5 to 7 days^¶	15 mg/kg orally divided 3 times per day for 5 to 7 days (maximum 250 mg per dose)
Albendazole	400 mg orally once daily for 5 days	10 to 15 mg/kg orally once daily for 5 days (maximum 400 mg per dose)
Mebendazole	200 mg orally 3 times per day for 5 days	200 mg orally 3 times per day for 5 days
Paromomycin^§	10 mg/kg orally 3 times per day for 5 to 10 days	10 mg/kg orally 3 times per day for 5 to 10 days
Furazolidone^¥	100 mg orally 4 times per day for 7 to 10 days	2 mg/kg orally 4 times per day for 7 to 10 days (maximum 100 mg per dose)
Quinacrine	100 mg orally 3 times per day for 5 days	2 mg/kg orally 3 times per day for 5 days (maximum 100 mg per dose)^‡

Refer to the UpToDate text for additional information regarding choice of therapy, approach to recurrent or refractory infection, and drug availability.

* Tinidazole has US Food and Drug Administration (FDA) approval for treatment of giardiasis in patients >3 years of age.
¶ Patients should be counseled to avoid alcohol consumption while taking tinidazole or metronidazole.
Δ Nitazoxanide has FDA approval for treatment of giardiasis in patients >1 year of age.
◊ For lactating women, an alternative approach to metronidazole dosing consists of 2 g single dose (with interruption of breastfeeding for 12 to 24 hours); this approach is extrapolated from the approach to treatment of Trichomonas. Thus far, no reports of untoward effects in breastfed infants have been published with either dosing approach.^[1]
§ Poor intestinal absorption; it may be useful for treatment of giardiasis in pregnancy.
¥ Potentially significant drug and food interactions with use greater than 5 days due to monoamine oxidase inhibition. Refer to drug information section for additional information.
‡ Use of quinacrine for treatment of giardiasis is reserved for refractory cases.

Reference:

Hale T, Rowe HE. Medications & Mothers' Milk: A Manual of Lactational Pharmacology, 16th ed. Hale Publishing, Amarillo, TX 2014. p.724.

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