From the Guidelines
The drug of choice for treating giardiasis in adults is Tinidazole, which inhibits pyruvate-ferredoxin oxidoreductase, as recommended by the 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea 1. This mechanism of action is central to how Tinidazole effectively treats this parasitic infection. When Tinidazole enters Giardia lamblia, the anaerobic parasite that causes giardiasis, it is reduced to form reactive metabolites. These metabolites interfere with pyruvate-ferredoxin oxidoreductase, an enzyme crucial for the parasite's energy metabolism. By inhibiting this enzyme, Tinidazole disrupts the parasite's ability to generate energy, ultimately leading to its death. Some key points to consider when treating giardiasis include:
- Tinidazole is approved in the United States for children aged ≥3 years and is available in tablets that can be crushed 1.
- Metronidazole, an alternative treatment, has a high frequency of gastrointestinal side effects and is not FDA approved for the treatment of giardiasis 1.
- The recommended treatment regimen for Tinidazole is a single 2-gram dose, which works through the same mechanism as metronidazole, making it a more convenient option for patients 1.
From the FDA Drug Label
The nitro-group of tinidazole is reduced by cell extracts of Trichomonas. The free nitro radical generated as a result of this reduction may be responsible for the antiprotozoal activity. Chemically reduced tinidazole was shown to release nitrites and cause damage to purified bacterial DNA in vitro Additionally, the drug caused DNA base changes in bacterial cells and DNA strand breakage in mammalian cells. The mechanism by which tinidazole exhibits activity against Giardia and Entamoeba species is not known.
The mechanism of action for tinidazole, the drug of choice used in the treatment of giardiasis, is attacks microbial DNA via a toxic radical metabolite. This is because the nitro-group of tinidazole is reduced by cell extracts, generating a free nitro radical that may be responsible for the antiprotozoal activity, causing damage to purified bacterial DNA and DNA strand breakage in mammalian cells 2.
From the Research
Mechanism of Action for Giardiasis Treatment
The drug of choice for treating giardiasis is metronidazole or tinidazole. The mechanism of action for these drugs is:
- Attacks microbial DNA via a toxic radical metabolite 3, 4 This is the primary mechanism by which metronidazole and tinidazole exert their effect on Giardia duodenalis.
Alternative Treatments
Other treatments for giardiasis include:
- Albendazole: Inhibits microtubule polymerization, but its effectiveness against Giardia is not as well established as metronidazole or tinidazole 5, 6, 7
- Nitazoxanide: Inhibits pyruvate-ferredoxin oxidoreductase, an enzyme essential for the survival of Giardia 5, 4
Comparison of Treatments
Studies have compared the effectiveness of different treatments for giardiasis, including: