Nitazoxanide (pronounced nye-ta-ZOX-a-nide) is a prescription medication primarily used to treat intestinal infections caused by parasites. In the United States, it is most commonly known by its brand name, Alinia.

While many antiparasitic drugs have been around for 50 years or more, nitazoxanide is relatively new to the medical scene (FDA approved in 2002). It is scientifically significant because it is the first member of a completely new class of drugs called thiazolides. It is valued by doctors for its “broad-spectrum” capabilities, meaning it is effective against a wide variety of organisms, ranging from microscopic single-celled protozoa to parasitic worms and even certain viruses.

What Is It Approved To Treat?

In the United States, the FDA has officially approved nitazoxanide for the treatment of diarrhea caused by two specific waterborne parasites:

1. Cryptosporidium parvum: A microscopic parasite that has a tough outer shell, allowing it to survive outside the body for long periods and making it very tolerant to chlorine disinfection in pools and water systems.
2. Giardia lamblia: One of the most common intestinal parasites worldwide, often contracted by drinking contaminated water (camping streams) or through close contact in daycare centers.

One of the drug’s key advantages is its safety profile for children. Unlike some stronger antibiotics or antiparasitics that are restricted to adults, nitazoxanide is available in a liquid suspension (usually strawberry-flavored) and is approved for children as young as 12 months old.

How Does It Work? (The Mechanism)

Nitazoxanide works differently than antibiotics. Instead of destroying the cell wall of the invader, it attacks its metabolism.

When a patient takes the drug, their body converts it into an active chemical called tizoxanide. This chemical targets a specific enzyme in the parasite called pyruvate:ferredoxin oxidoreductase (PFOR).

Simple parasites rely on this PFOR enzyme to transfer electrons and generate energy in low-oxygen environments (like the human gut). Nitazoxanide essentially “blocks the wire” of this electron transfer. Without the ability to move electrons, the parasite’s energy metabolism collapses, and it dies.

Because human cells do not use the PFOR enzyme for energy, the drug can kill the parasite without disrupting the patient’s own cellular functions.

Beyond Parasites: Antiviral Research

One of the most intriguing aspects of nitazoxanide is its potential antiviral properties. It is known as a “host-directed” antiviral.

Rather than attacking a virus directly, nitazoxanide appears to boost the host cell’s ability to detect and fight the virus. Research suggests it inhibits the production of viral proteins, preventing the virus from assembling new copies of itself.

Because of this mechanism, nitazoxanide has been studied for use against:

• Rotavirus & Norovirus: Common causes of viral gastroenteritis (stomach flu).
• Influenza: Clinical trials have explored its ability to shorten the duration of the flu.
• Hepatitis B and C.
• Respiratory Viruses: It has been a subject of study for broad respiratory viral infections, though it is not currently a standard-of-care treatment for them outside of clinical trials.

Side Effects and Characteristics

Nitazoxanide is generally well-tolerated, but like all medications, it has side effects.

• Digestive Issues: The most common side effects are stomach pain, nausea, and occasionally mild diarrhea.
• Urine Discoloration: A unique but harmless side effect is that it can cause urine (and sometimes the whites of the eyes) to turn a bright yellow or greenish tint. This resolves once the medication is stopped.
• Taste: The tablets are known to have a metallic aftertaste.