eMedicine Specialties > Pediatrics: General Medicine > Parasitology

Giardiasis: Treatment & Medication

Author: Murat Hökelek, MD, PhD, Technical Consultant of Parasitology Laboratory, Associate Professor, Department of Clinical Microbiology, Ondokuz Mayis University Medical School, Turkey
Coauthor(s): Michael D Nissen, MBBS, BMedSc, FRACP, FRCPA, Associate Professor in Biomolecular, Biomedical Science & Health, Griffith University; Director of Infectious Diseases and Unit Head of Queensland Paediatric Infectious Laboratory, Sir Albert Sakzewski Viral Research Centre, Royal Children's Hospital
Contributor Information and Disclosures

Updated: Dec 17, 2008

Treatment

Medical Care

Treat children with acute or chronic diarrhea who manifest a failure to thrive, malabsorption, or other GI tract symptoms in whom Giardia organisms have been identified31 .

  • Generally, do not treat asymptomatic persons who excrete the organism, except to prevent household transmission (eg, from toddlers to pregnant women or to patients with hypogammaglobulinemia or cystic fibrosis) and to permit adequate treatment in individuals with possible Giardia intestinalis –associated antibiotic malabsorption who require oral antibiotic treatment for other infections.20,32
  • Routine treatment of infected persons in highly endemic areas where water supplies continue to be contaminated is of questionable value because reinfection may readily occur.11,33
  • Treat all infected persons who are in nonendemic areas.34
  • Appropriate fluid and electrolyte management is critical, particularly in patients with large-volume diarrheal losses.2

Consultations

Consultations with pediatric infectious disease specialists, parasitologists, and pediatric gastroenterologists are recommended.

Medication

Antiprotozoal agents

The 3 major classes of drugs that have proven benefit in the treatment of giardiasis are nitroimidazole derivatives, acridine dyes (eg, quinacrine), and nitrofurans (eg, furazolidone).

Although most experts recommend metronidazole and tinidazole as the drugs of choice because the brief treatment periods encourage good patient adherence, treatment failures occur in as many as 20% of cases. In posttreatment stool testing, treatment failure occurs when the parasite is probably resistant to metronidazole. Therefore, treatment with a second-line drug (eg, mepacrine, furazolidone) may be necessary.

The effectiveness of quinacrine is similar to that of nitroimidazole derivatives; however, it is less tolerated because of its adverse effects. These include the following: mild and transient headache, dizziness, and GI complaints (diarrhea, anorexia, nausea, abdominal cramps, vomiting [rare]), pleomorphic skin eruptions, and neuropsychiatric disturbances (nervousness, vertigo, irritability, emotional change, nightmares, transient psychosis).

Furazolidone is the least effective antigiardial drug but is widely used to treat children in the United States, partly because it is available as a suspension.

Nitazoxanide was approved for the treatment of children who had giardiasis in 2003. The drug interferes with anaerobic energy metabolism by inhibiting the pyruvate-ferredoxin oxidoreductase enzyme–dependent electron transfer.35,34,31


Metronidazole (Flagyl)

Imidazole ring–based antibiotic active against various anaerobic bacteria and protozoa. Used in combination with other antimicrobial agents (except for Clostridium difficile enterocolitis).

Adult

250 mg PO tid for 5 d

Pediatric

15 mg/kg/d PO divided tid for 5 d; not to exceed 750 mg/d

May increase toxicity of anticoagulants, lithium, and phenytoin; cimetidine may increase toxicity; disulfiram reaction may occur with ingested ethanol

Documented hypersensitivity; first trimester of pregnancy

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Do not use during first trimester of pregnancy; adjust dose in hepatic disease; monitor for seizures and development of peripheral neuropathy


Furazolidone (Furoxone)

PO anti-infective agent of the oxazolidine class used to treat bacterial or protozoal diarrhea and enteritis. May help in traveler's diarrhea, cholera, and bacteremic salmonellosis. Is bactericidal by interfering with several bacterial enzyme systems. Structurally similar to MAOIs and has MAOI activity. Approved by FDA in 1955.

Adult

100 mg tab or susp PO qid for 7-10 d

Pediatric

<1 month: Not recommended
>1 month: 5-8.8 mg/kg/d PO divided qid for 10 d; not to exceed 400 mg/d

Concurrent use with ethanol can cause disulfiramlike reaction; effectiveness and adverse effects of levodopa can increase if used concomitantly; agitation, seizures, diaphoresis, fever, coma, or apnea can occur with concomitant meperidine; increased pressor effects expected if administered with sympathomimetics (can cause release of large amounts of norepinephrine); concurrent use with tricyclic antidepressants can produce hypertension, hyperpyrexia, seizures, tachycardia, and acute psychosis

Documented hypersensitivity; G-6-PD deficiency

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Structurally similar to MAOIs and has MAOI activity; orthostatic hypotension and hypoglycemia may occur


Quinacrine (Atabrine)

Indicated to treat giardiasis and cestodiasis. Occasionally used to treat and suppress malaria.

Adult

100 mg PO tid for 5-7 d

Pediatric

7 mg/kg/d PO divided tid pc for 5 d; not to exceed 300 mg/d

Documented hypersensitivity; pregnancy; increases toxicity of primaquine (do not coadminister)

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Caution in hepatic disease, alcoholism, or with known hepatotoxic drugs; periodically assess CBC count in prolonged therapy; if a severe blood disorder not attributable to the treated disease occurs, consider discontinuation; caution in G-6-PD deficiency; instruct patients receiving prolonged therapy to promptly report any visual disturbances and perform periodic complete ophthalmologic examinations


Albendazole (Albenza)

Poorly absorbed from GI tract because of its low aqueous solubility. Concentrations negligible or undetectable in plasma because it is rapidly converted to the sulfoxide metabolite before reaching systemic circulation; systemic anthelmintic activity attributed to primary metabolite, albendazole sulfoxide; PO bioavailability appears to be enhanced when coadministered with a fatty meal (with estimated fat content of 40 g), as evidenced by higher (ie, <5-fold on average) plasma concentrations of albendazole sulfoxide compared to the fasted state.

Adult

400 mg PO qd for 5 d

Pediatric

15 mg/kg/d PO divided bid for 5 d

Coadministration with carbamazepine may decrease effectiveness; dexamethasone, cimetidine, and praziquantel may increase toxicity

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Discontinue use if LFT levels increase significantly (resume when levels decrease to pretest values); abdominal pain, nausea, vomiting, diarrhea, dizziness, vertigo, fever, increased intracranial pressure, and alopecia may occur


Nitazoxanide (Alinia)

Inhibits growth of C parvum sporozoites and oocysts and G lamblia trophozoites. Elicits antiprotozoal activity by interfering with pyruvate-ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reaction, which is essential to anaerobic energy metabolism. Available as a 20-mg/mL oral susp.

Adult

500 mg PO bid for 3 d

Pediatric

<1 year: Not established
1-4 years: 100 mg (5 mL) PO q12h for 3 d with food
4-11 years: 200 mg (10 mL) PO q12h for 3 d with food
>11 years: 500 mg PO bid for 3 d

Tizoxanide (nitazoxanide metabolite) is >99.9% bound to plasma protein and may potentially increase toxicity of other highly plasma protein–bound drugs

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

May cause abdominal pain, diarrhea, vomiting, or headache; administer with food; caution when coadministered with other highly plasma protein–bound drugs with narrow therapeutic indices


Tinidazole (Fasigyn, Tindamax)

Nitroimidazole antiprotozoal agent. The mechanism by which tinidazole exhibits activity against Giardia and Entamoeba species is not known. Indicated to treat giardiasis in adults and children >3 y.

Adult

2 g PO once with food

Pediatric

<3 years: Not established
>3 years: 50 mg/kg PO once with food; not to exceed 2 g/dose

Limited data exist; interaction information based on experience with other nitroimidazole derivatives (ie, metronidazole); may prolong PT when coadministered with warfarin; avoid alcoholic beverages and preparations containing ethanol or propylene glycol during and 3 d following administration (may cause disulfiramlike reaction); may increase serum levels of lithium, phenytoin, cyclosporine, tacrolimus, and fluorouracil; CYP450 inducers (eg, phenobarbital, rifampin, phenytoin) may increase elimination; CYP450 inhibitors (eg, cimetidine, ketoconazole) may decrease elimination; concurrent administration with cholestyramine may decrease oral bioavailability; oxytetracycline may antagonize effect

Documented hypersensitivity; first trimester of pregnancy

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Carcinogenicity has been observed in mice and rats treated chronically with metronidazole (another nitroimidazole), although not observed with tinidazole, use cautiously; seizures and peripheral neuropathy have been reported; caution in history of blood dyscrasia; may cause metallic/bitter taste, nausea, anorexia, vomiting, weakness, fatigue, dizziness, or headache; if administered on day of hemodialysis, administer additional dose equivalent to half of recommended dose following dialysis

More on Giardiasis

Overview: Giardiasis
Differential Diagnoses & Workup: Giardiasis
Treatment & Medication: Giardiasis
Follow-up: Giardiasis
Multimedia: Giardiasis
References
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Further Reading

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Keywords

giardiasis, Giardia, Giardia lamblia, Giardia duodenalis, Giardia intestinalis, protozoal diarrhea, steatorrhea, malabsorption, lambliasis, chronic diarrhea, vomiting, nausea, irritability, sleep disorder, mental depression, neuroasthenia, urticaria, abdominal cramps, contaminated food, food poisoning

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Contributor Information and Disclosures

Author

Murat Hökelek, MD, PhD, Technical Consultant of Parasitology Laboratory, Associate Professor, Department of Clinical Microbiology, Ondokuz Mayis University Medical School, Turkey
Murat Hökelek, MD, PhD is a member of the following medical societies: Turkish Society for Parasitology
Disclosure: Nothing to disclose.

Coauthor(s)

Michael D Nissen, MBBS, BMedSc, FRACP, FRCPA, Associate Professor in Biomolecular, Biomedical Science & Health, Griffith University; Director of Infectious Diseases and Unit Head of Queensland Paediatric Infectious Laboratory, Sir Albert Sakzewski Viral Research Centre, Royal Children's Hospital
Michael D Nissen, MBBS, BMedSc, FRACP, FRCPA is a member of the following medical societies: American Academy of Pediatrics, American Society for Microbiology, Pediatric Infectious Diseases Society, Royal Australasian College of Physicians, and Royal College of Pathologists of Australasia
Disclosure: Nothing to disclose.

Medical Editor

Glenn J Fennelly, MD, MPH, Director, Division of Pediatric Infectious Diseases, Jacobi Medical Center; Associate Professor, Department of Pediatrics, Albert Einstein College of Medicine
Glenn J Fennelly, MD, MPH is a member of the following medical societies: Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Martin Weisse, MD, Program Director, Associate Professor, Department of Pediatrics, West Virginia University
Martin Weisse, MD is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

CME Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Consulting; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching; sanofi pasteur Grant/research funds Unrestricted research grant; sanofi pasteur  Consulting; sanofi pasteur Honoraria Speaking and teaching; Tap Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

 
 
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