April 2008 · Vol. 57, No. 4: 270-271
From the Family Physicians Inquiries Network
What’s the most effective treatment for giardiasis?William Nichols, MLS
Eglin AFB Family Medicine Residency, Eglin AFB, Fla
A single 2-g dose of tinidazole is the best treatment (strength of recommendation [SOR]: A, based on meta-analysis). Other drugs, such as nitazoxanide, metronidazole, mebendazole, and albendazole, can also be used (SOR: A, based on randomized controlled trial [RCT] of patient-oriented outcomes), but tinidazole has a higher clinical cure rate than these drugs. It also has a comparable side-effect profile and requires only 1 dose.
The real challenge is diagnosis
University of Nevada, Reno
As this review points out, all the available treatments for giardiasis are effective. Additional prescribing considerations include cost (500 mg metronidazole costs about 30 cents, for example, while 2 mg tinidazole costs $18) and insurance coverage. Tinidazole and metronidazole, unlike the other medications, require that the patient abstain from alcohol for 72 hours after dosing.
In my experience, the biggest challenge in treating giardiasis is deciding when to consider it in the differential and when to test for it. Presentations vary from vague symptoms such as bloating to severe diarrhea. Often the patient has not been exposed to well or stream water. You can test stool samples for ova and parasites, or serum for fluorescent antibody or enzyme-linked immunosorbent assay (ELISA).
Prescribing considerations include cost:
Giardia lamblia is a protozoan parasite found worldwide. Infection typically results from ingesting cysts in contaminated food or water. Patients with giardiasis may be asymptomatic or have mild to severe gastrointestinal symptoms, including explosive diarrhea, abdominal pain, steatorrhea, flatulence, bloating, nausea, and vomiting. Treatment varies widely based on geographic location, physician preference, and availability and cost of medication (TABLE).1
Drugs commonly used to treat giardiasis
||Can be given to children 3 years of age and older Pregnancy drug class C
||250, 500,or 750 mg
||1 time or 3 times daily for 5 days. (Usually 250 mg, 3 times a day, for 5 days)
||Contraindicated in first trimester of pregnancy
||Twice daily for 5 days
||Contraindicated in first trimester of pregnancy Pregnancy drug class B
||Twice daily for 3 days
||Can be given to children 1 year of age and older Available in liquid form Pregnancy drug class B
||Twice daily for 5 days
||Pregnancy drug class C
Tinidazole is the treatment of choice
A 2006 Cochrane Review compared 34 trials of many drug therapies for giardiasis.2 The review, which is being updated to include additional publications, evaluated both head-to-head and placebo-controlled studies, looking at dosage as well as length of drug therapy.
The review found that a single dose of tinidazole had a higher clinical cure rate than other therapies such as metronidazole (odds ratio [OR]=5.33; 95% confidence interval [CI], 2.66-10.67)2 along with a comparable side-effect profile. These findings favor tinidazole as the treatment of choice for symptomatic giardiasis.
How effective are other drugs?
The 2006 Cochrane Review found no difference in clinical cure rate between short-term treatment (3 days) with metronidazole and longer therapy with metronidazole or other drugs. Subsequently, a single dose of metronidazole was found to be as effective as treatment for 5 days or longer (OR=0.33, 95% CI 0.08-1.34).
Since publication of the Cochrane review, several studies have further evaluated mebendazole.
The biggest challenge in treating giardiasis is deciding when to consider it in the differential and when to test for it
An RCT in Cuban children 5 to 15 years of age found no difference in clinical cure rate between a 5-day course of mebendazole and more traditional therapy with quinacrine.3
Another RCT comparing 5 days of mebendazole with 7 days of metronidazole in 7- to 12-year-old Iranian children showed no statistical difference in microbiologic cure between the 2 regimens.4
Single-dose tinidazole was superior to 3 doses of mebendazole in a single day in an RCT of 122 Cuban children that measured microbiologic cure (NNT=5.5 patients with tinidazole vs mebendazole).5
Two RCTs found nitazoxanide to be effective (number needed to treat [NNT]=1.82) compared to placebo in adolescents and adults.6 A 3-day course of nitazoxanide was as effective as 5 days of metronidazole (80% vs 85%, P=0.61) in resolving clinical giardiasis.7
An RCT of albendazole, 400 mg for 5 days, in 28 adults found it to be as effective as 500 mg metronidazole given 3 times a day for 5 days (80% vs 83%) but less likely than metronidazole (2% vs 18%) to cause anorexia (number needed to harm [NNH]=6.25).
The Centers for Disease Control and Prevention recommends tinidazole, metronidazole, quinacrine, albendazole, or nitazoxanide to treat giardiasis; however, it doesn’t indicate a preference for 1 medicine over another.1 The Infectious Diseases Society of America has no guideline. The Sanford Guide to Antimicrobial Therapy recommends either a single 2-g dose of tinidazole or 500 mg of nitazoxanide PO bid for 3 days as primary treatment.8
The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Air Force Medical Service, nor the US Air Force.
- Beach M.
Prevention of specific infectious diseases—giardiasis. In: Arguin PM, Kozarsky PE, Navin AW eds. Centers for Disease Control and Prevention. Health Information for International Travel 2005-2006. Atlanta: US Department of Health and Human Services, Public Health Service; 2005. Available at: www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=dis&obj=giardiasis.htm. Accessed March 7, 2008.
- Zaat JO,
Drugs for treating giardiasis. Cochrane Database Syst Rev. 2005:CD000217.
- Canete R,
Gonzalez M, et al. Randomized clinical study of five days’ therapy with mebendazole compared to quinacrine in the treatment of symptomatic giardiasis in children. World J Gastroenterol. 2006;12:6366–6370.
- Sadjjadi SM,
Comparative clinical trial of mebendazole and metronidazole in giardiasis of children. J Trop Pediatr. 2001;47:176–178.
- Canete R,
Gonzalez M, et al. A randomized, controlled, open-label trial of a single day of mebendazole versus a single dose of tinidazole in the treatment of giardiasis in children. Curr Med Res Opin. 2006;22:2131–2136.
- Rossignol JF,
Ayers MS, et al. Treatment of diarrhea caused by Giardia intestinalis and Entameba histolytica or E dispar: A Randomized, double-blind, placebo-controlled study of nitazoxanide. J Infect Dis. 2001;184:381–384.
- Ortiz JJ,
Gargala G, et al. Randomized clinical study of nitazoxanide compared to metronidazole in the treatment of symptomatic giardiasis in children from northern Peru. Aliment Pharmacol Ther. 2001;15:1409–1415.
- Gilbert DM,
Moellering RC, et al. The Sanford Guide to Antimicrobial Therapy 2006. 36th ed. Sperryville, Va: Antimicrobial Therapy; 2006:95.
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