Which medications in the drug class Antibiotics are used in the treatment of Giardiasis?

Updated: Oct 01, 2018
  • Author: Hisham Nazer, MBBCh, FRCP, DTM&H; Chief Editor: Burt Cagir, MD, FACS  more...
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The therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting. [60] 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.

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.

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.

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.

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.


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.


This agent, available as an orphan drug in the United States 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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