What's the Most Effective Treatment for Giardiasis?

From the CLINICAL INQUIRIES Family Physicians Inquiries Network

Jeffrey D. Kiser, MD, and Christopher P. Paulson, MD, What’s the most effective FAAFP Eglin AFB Family Medicine treatment for giardiasis? Residency, Eglin AFB, Fla

Evidence-based answer A single 2-g dose of tinidazole is the best based on randomized controlled trial treatment (strength of recommendation [RCT] of patient-oriented outcomes), [SOR]: A, based on meta-analysis). but tinidazole has a higher clinical Other drugs, such as nitazoxanide, cure rate than these drugs. It also has metronidazole, mebendazole, and a comparable side-effect profi le and albendazole, can also be used (SOR: A, requires only 1 dose. Clinical commentary® Dowden Health Media The real challenge is diagnosis challenge in treating giardiasis is deciding AsCopyright this reviewFor points personalout, all the available use whenonly to consider it in the differential and treatments for giardiasis are effective. when to test for it. Presentations vary Additional prescribing considerations from vague symptoms such as bloating include cost (500 mg metronidazole costs to severe diarrhea. Often the patient FAST TRACK about 30 cents, for example, while 2 has not been exposed to well or stream Prescribing mg tinidazole costs $18) and insurance water. You can test stool samples for ova coverage. Tinidazole and metronidazole, and parasites, or serum for fl uorescent considerations unlike the other medications, require that antibody or enzyme-linked immunosorbent include cost: the patient abstain from alcohol for 72 assay (ELISA). hours after dosing. ❙ 500 mg Cynthia Brown, MD metronidazole In my experience, the biggest University of Nevada, Reno costs 30 cents ❙ 2 mg ❚ Evidence summary Tinidazole is the tinidazole Giardia lamblia is a protozoan para- treatment of choice site found worldwide. Infection typi- A 2006 Cochrane Review compared 34 costs $18 cally results from ingesting cysts in trials of many drug therapies for giardia- contaminated food or water. Patients sis.2 The review, which is being updated with giardiasis may be asymptomatic to include additional publications, evalu- or have mild to severe gastrointestinal ated both head-to-head and placebo-con- symptoms, including explosive diar- trolled studies, looking at dosage as well rhea, abdominal pain, steatorrhea, fl at- as length of drug therapy. ulence, bloating, nausea, and vomiting. The review found that a single dose of Treatment varies widely based on geo- tinidazole had a higher clinical cure rate graphic location, physician preference, than other therapies such as metronidazole and availability and cost of medication (odds ratio [OR]=5.33; 95% confi dence (TABLE).1 interval [CI], 2.66-10.67)2 along with a

270 VOL 57, NO 4 / APRIL 2008 THE JOURNAL OF FAMILY PRACTICE

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270_JFP0408 270 3/19/08 9:34:02 AM TABLE 1 Drugs commonly used to treat giardiasis

DRUG ADULT DOSE SCHEDULE COMMENT Tinidazole 2 g 1 time Can be given to children 3 years of age and older Pregnancy drug class C Metronidazole 250, 500, 1 time or 3 Contraindicated in fi rst trimester of pregnancy or 750 mg times daily for 5 days. (Usually 250 mg, 3 times a day, for 5 days) Mebendazole 100 mg Twice daily Contraindicated in fi rst trimester of pregnancy for 5 days Pregnancy drug class B Nitazoxanide 500 mg Twice daily Can be given to children 1 year of age and older for 3 days Available in liquid form Pregnancy drug class B Albendazole 200-400 mg Twice daily Pregnancy drug class C for 5 days Giardia lamblia Sources: Beach M,1 and Gilbert DM et al.8

comparable side-effect profi le. These fi nd- measured microbiologic cure (NNT=5.5 ings favor tinidazole as the treatment of patients with tinidazole vs mebendazole).5 choice for symptomatic giardiasis. Two RCTs found nitazoxanide to be effective (number needed to treat How effective are other drugs? [NNT]=1.82) compared to placebo in The 2006 Cochrane Review found no adolescents and adults.6 A 3-day course of difference in clinical cure rate between nitazoxanide was as effective as 5 days of short-term treatment (3 days) with metronidazole (80% vs 85%, P=0.61) in FAST TRACK metronidazole and longer therapy with resolving clinical giardiasis.7 The biggest metronidazole or other drugs. Subse- An RCT of albendazole, 400 mg for quently, a single dose of metronidazole 5 days, in 28 adults found it to be as ef- challenge in was found to be as effective as treatment fective as 500 mg metronidazole given treating INC. for 5 days or longer (OR=0.33, 95% CI 3 times a day for 5 days (80% vs 83%) giardiasis is 0.08-1.34). but less likely than metronidazole (2% vs deciding when Since publication of the Cochrane 18%) to cause anorexia (number needed

RESEARCHERS, review, several studies have further evalu- to harm [NNH]=6.25). to consider it

ated mebendazole. in the differential PHOTO / • An RCT in Cuban children 5 to 15 Recommendations and when to years of age found no difference in clini- The Centers for Disease Control and OTTAWA cal cure rate between a 5-day course of Prevention recommends tinidazole, met- test for it

mebendazole and more traditional thera- ronidazole, quinacrine, albendazole, or NICOLE / py with quinacrine.3 nitazoxanide to treat giardiasis; how- • Another RCT comparing 5 days of ever, it doesn’t indicate a preference for MECKES mebendazole with 7 days of metronida- 1 medicine over another.1 The Infec-

OLIVER zole in 7- to 12-year-old Iranian children tious Diseases Society of America has

showed no statistical difference in micro- no guideline. The Sanford Guide to An- 4 CREDIT: biologic cure between the 2 regimens. timicrobial Therapy recommends either

2008 • Single-dose tinidazole was superior a single 2-g dose of tinidazole or 500 mg © to 3 doses of mebendazole in a single day of nitazoxanide PO bid for 3 days as pri- 8 ■ PHOTO in an RCT of 122 Cuban children that mary treatment.

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