Nitazoxanide
Other antiprotozoals
Other antiprotozoals
Oral broad-spectrum antiparasitic for diarrhoea caused by Giardia and Cryptosporidium; well tolerated, it may tint the urine.
Quick facts
- Group
- Other antiprotozoals
- Target
- Pyruvate-ferredoxin oxidoreductase (PFOR) of anaerobic protozoa and bacteria
- Used for
- Diarrhoea caused by Giardia · Intestinal amoebiasis
- Key effects
- Abdominal pain · Headache · Nausea
- Monitor
- Number of stools and hydration
- ATC
- P01AX11
No doses: the clinician sets them by the current guideline.
Mechanism of action
A nitrothiazolyl-salicylamide. In the gut it is quickly hydrolysed to tizoxanide, its active metabolite. Tizoxanide interferes with the electron-transfer reaction of pyruvate-ferredoxin oxidoreductase (PFOR), an enzyme that anaerobic protozoa such as Giardia and Cryptosporidium need to make energy from pyruvate; humans do not use this enzyme. It also acts on Entamoeba histolytica, some helminths and some anaerobic bacteria.
- Hydrolysed to active tizoxanide
- Blocks electron transfer by PFOR
- Anaerobic energy metabolism fails
- Giardia and Cryptosporidium die
Indications
- Diarrhoea caused by Giardia in adults and children over one year Giardiasis →
- Diarrhoea caused by Cryptosporidium in immunocompetent people (less effective in immunocompromised people) Cryptosporidiosis and other intestinal coccidia (Cyclospora, Cystoisospora) →
- Intestinal amoebiasis and mixed intestinal parasitic infections (off-label use) Intestinal amoebiasis (amoebic dysentery) →
Adverse effects
Common
- Abdominal pain
- Headache
- Nausea
- Discoloured (greenish-yellow) urine
Contraindications
- Hypersensitivity to nitazoxanide
- Caution: liver or kidney disease
Key interactions
- Other medicines and supplements
- No major interactions are named in patient information; all medicines are still reviewed before starting
What is monitored
- Number of stools and hydration
- Clinical response after the short course; in immunocompromised people, response is often incomplete
- Stool tests when diarrhoea persists
Administration and safety
- Oral tablets or suspension, with food, as a short course.
- The suspension is shaken well; unused suspension is discarded after a set number of days.
- Fluids are given to prevent dehydration.
Pregnancy and breastfeeding
Generally considered low risk in pregnancy, but human data are limited and the prescriber weighs the need.
Nursing care
- Assess hydration (weight, urine output, mucous membranes) in children with diarrhoea.
- Explain that the urine may change colour and that this is harmless.
- Teaching: drink plenty of fluids, finish the course and wash hands well to avoid spreading the parasite.
- Report persistent diarrhoea, especially in people with HIV or other immune problems.
Pharmacokinetics
- Absorption
- Oral; rapidly converted to tizoxanide; taken with food
- Distribution
- Tizoxanide is more than 99.9 % bound to plasma proteins
- Metabolism
- Hydrolysis to tizoxanide, then glucuronide conjugation
- Elimination
- Urine, bile and faeces
Test yourself
Think of the answer, then tap the question to see it.
Which two protozoa are nitazoxanide's main targets?
Giardia (giardiasis) and Cryptosporidium (cryptosporidiosis).
Which enzyme does its active metabolite inhibit?
Pyruvate-ferredoxin oxidoreductase (PFOR), needed for the energy metabolism of anaerobic protozoa.
In which patients is it less effective against Cryptosporidium?
In immunocompromised people, such as those with advanced HIV; restoring immune function is the key measure.
Connections
← Back to the class: Other antiprotozoals
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Nitazoxanide: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.