Giardiasis Medication

  • Author: Sandeep Mukherjee, MB, BCh, MPH, FRCPC; Chief Editor: Julian Katz, MD   more...
 
Updated: Jun 29, 2011
 

Medication Summary

Antibiotic therapy is standard in the treatment of giardiasis.[43, 59] Antimicrobial resistance has been reported.

Metronidazole is the antimicrobial agent most commonly used in the treatment of giardiasis in the United States. It has a cure rate of 85-90%.

Tinidazole is now approved in the United States and is considered a first-line agent outside the United States. It is given in a single dose, the efficacy is reported at 90%, and it is believed to have fewer side effects than metronidazole. A common adverse effect is GI upset.

Paromomycin has been recommended for use in pregnancy because systemic absorption is low, but the cure rate is lower than with other agents.

Some drugs not available in the United States are considered effective therapeutic alternatives. Quinacrine achieves a cure rate of 90-95% but is available as an orphan drug in the US. The most common adverse effects include nausea, vomiting, and abdominal cramping. Occasional yellow discoloration of the skin, urine, and sclerae may occur. This medication should not be used in patients with documented hypersensitivity to this medication or related products, those diagnosed with psoriasis, or those with a history of psychosis.

Therapy for asymptomatic individuals should be initiated if the risk of reinfection is low. This reduces the risk of transmission to others and the potential development of later clinical infection or chronic disease.

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Antibiotics

Class Summary

The therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.[55] The 2 major classes of drugs that have proven benefit in the treatment of giardiasis are nitroimidazole derivatives and acridine dyes.

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, probably because of resistance. Therefore, treatment with a second-line drug (eg, mepacrine) 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).

Nitazoxanide is approved by the US Food and Drug Administration for the treatment of children and adults for diarrhea from giardiasis.

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Metronidazole (Flagyl)

 

Metronidazole is a nitroimidazole that, once concentrated within the organism, is reduced by intracellular electron transport proteins. The formation of free radicals causes disruption of cellular elements and subsequent death of the organism. It is the most commonly prescribed antibiotic for giardiasis. The recommended adult dose is 250 mg PO tid for 5-7 days.

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Albendazole (Albenza)

 

This agent decreases adenosine triphosphate (ATP) production in worms, causing energy depletion, immobilization, and, finally, death. To avoid an inflammatory response in CNS, the patient also must be started on anticonvulsants and high-dose glucocorticoids.

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Nitazoxanide (Alinia)

 

This agent inhibits growth of Cryptosporidium parvum sporozoites and oocysts and Giardia lamblia trophozoites. It elicits antiprotozoal activity by interfering with pyruvate-ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reaction, which is essential to anaerobic energy metabolism. It is available as a 20-mg/mL oral suspension.

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Tinidazole (Tindamax)

 

Tinidazole is a nitroimidazole antiprotozoal agent. The mechanism by which tinidazole exhibits activity against Giardia and Entamoeba species is not known. The recommended adult dose is 2 g PO once; for children, the recommended dose is 50 mg/kg PO once.

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Paromomycin

 

Paromomycin is a poorly absorbed aminoglycoside that may be considered for use in severe infection in pregnant patients. The most common adverse effects include nausea, increased GI motility, abdominal pain, and diarrhea.

Quinacrine

 

This agent, available as an orphan drug in the US is indicated to treat giardiasis and cestodiasis. It is occasionally used to treat and suppress malaria. The recommended adult dose is 100 mg PO tid for 5-7 d; for children, the recommended dose is 2 mg/kg PO tid for 5-7 d.

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Contributor Information and Disclosures
Author

Sandeep Mukherjee, MB, BCh, MPH, FRCPC  Associate Professor, Department of Internal Medicine, Section of Gastroenterology and Hepatology, University of Nebraska Medical Center; Consulting Staff, Section of Gastroenterology and Hepatology, Veteran Affairs Medical Center

Sandeep Mukherjee, MB, BCh, MPH, FRCPC is a member of the following medical societies: Royal College of Physicians and Surgeons of Canada

Disclosure: Merck Honoraria Speaking and teaching; Ikaria Pharmaceuticals Honoraria Board membership

Coauthor(s)

Andre Pennardt, MD, FACEP, FAAEM, FAWM  Clinical Associate Professor of Emergency Medicine, Medical College of Georgia; Assistant Professor of Military and Emergency Medicine, Uniformed Services University of the Health Sciences; Consulting Staff, Departments of Emergency Medicine, Aviation Medicine and Dive Medicine, Womack Army Medical Center

Andre Pennardt, MD, FACEP, FAAEM, FAWM is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, Association of Military Surgeons of the US, International Society for Mountain Medicine, National Association of EMS Physicians, Special Operations Medical Association, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Barry J Sheridan, DO  Chief Warrior in Transition Services, Brooke Army Medical Center

Barry J Sheridan, DO is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Murat Hökelek, MD, PhD  Technical Consultant of Parasitology Laboratory, 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.

Glenn Fennelly, MD, MPH  Director, Division of Infectious Diseases, Lewis M Fraad Department of Pediatrics, Jacobi Medical Center; Clinical Associate Professor of Pediatrics, Albert Einstein College of Medicine

Glenn Fennelly, MD, MPH is a member of the following medical societies: Pediatric Infectious Diseases Society

Disclosure: Nothing to disclose.

Mark H Johnston, MD  Associate Professor of Medicine, Uniformed Services University of Health Sciences; Consulting Staff, Lancaster Gastroenterology Inc

Mark H Johnston, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, and Christian Medical & Dental Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Manoop S Bhutani, MD  Professor, Co-Director, Center for Endoscopic Research, Training and Innovation (CERTAIN), Director, Center for Endoscopic Ultrasound, Department of Medicine, Division of Gastroenterology, University of Texas Medical Branch; Director, Endoscopic Research and Development, The University of Texas MD Anderson Cancer Center

Manoop S Bhutani, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Institute of Ultrasound in Medicine, and American Society for Gastrointestinal Endoscopy

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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: Nothing to disclose.

Steven C Dronen, MD, FAAEM  Chair, Department of Emergency Medicine, LeConte Medical Center

Steven C Dronen, MD, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Julian Katz, MD  Clinical Professor of Medicine, Drexel University College of Medicine

Julian Katz, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Geriatrics Society, American Medical Association, American Society for Gastrointestinal Endoscopy, American Society of Law, Medicine & Ethics, American Trauma Society, Association of American Medical Colleges, and Physicians for Social Responsibility

Disclosure: Nothing to disclose.

Acknowledgments

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors Brooks D Cash, MD, FACP, and Michael D Nissen, MBBS, FRACP, FRCPA,to the development and writing of the source article.

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Giardia lamblia, cyst form.
Giardia lamblia trophozoites in culture.
A Giardia intestinalis cyst.
Giardia intestinalis trophozoites on stool examination from a patient with diarrhea.
Giardia trophozoite
Giardia cyst.
 
 
 
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