tizoxanide

Tizoxanide is the principal active metabolite of nitazoxanide, a broad-spectrum antiparasitic and antiviral agent used to treat intestinal infections caused by Giardia lamblia and Cryptosporidium parvum, as well as certain helminth infections. After oral administration of nitazoxanide, it is rapidly deacetylated in the gut wall and liver to tizoxanide, which then circulates systemically to exert pharmacologic effects. Tizoxanide itself is not typically marketed as a separate drug.

Mechanism of action: Tizoxanide inhibits the pyruvate:ferredoxin oxidoreductase enzyme-dependent electron transfer reaction, a key energy pathway in anaerobic protozoa and some helminths, limiting their growth. The antiviral activity attributed to nitazoxanide is thought to involve interference with host cell processes required for viral replication; tizoxanide is the active moiety contributing to these effects.

Pharmacokinetics and safety: Tizoxanide is formed in vivo from nitazoxanide, with elimination via urine and feces. It is highly bound to plasma proteins. Adverse effects are generally mild and include gastrointestinal symptoms such as abdominal pain, nausea, and diarrhea; rare hypersensitivity or hepatotoxicity may occur.

Regulatory status and use: Therapeutic use centers on nitazoxanide formulations; tizoxanide is the active circulating metabolite. As such, information about tizoxanide-specific dosing is limited, and clinicians refer to nitazoxanide labeling. The compound is primarily of interest in pharmacology and drug development contexts.