Zoxanid

Approved Indications:

• Treatment of diarrhea and enteritis caused by Giardia lamblia.
• Treatment of diarrhea and enteritis due to Cryptosporidium parvum in immunocompetent adults and children ≥ 1 year.

Clinically Accepted Off‑Label Uses:

• Amebiasis (Entamoeba histolytica), when first-line therapy is not tolerated.
• Helicobacter pylori infection: as part of multidrug regimens in some regions.
• Emerging evidence for use in Norovirus gastroenteritis, rotavirus, and cell-culture–based off-label use in COVID‑19 (limited, not routinely recommended outside studies).

Formulations: Oral suspension (100 mg/5 mL), tablets (500 mg)

Adults and Children ≥ 12 years:

• 500 mg orally twice daily with food for 3 days (standard course for parasitic diarrhea).

Children 1–11 years (Body weight–based):

• 100–200 mg orally twice daily for 3 days, based on weight.
• Suspension preferred for younger children.

Elderly:

• No dose adjustment; treat like adults.

Hepatic Impairment:

• Mild to moderate: no adjustment needed.
• Severe: use with caution; limited data.

Renal Impairment:

• Not clinically significant; no adjustment required.

Nitazoxanide is converted to its active metabolite tizoxanide, which interferes with pyruvate:ferredoxin oxidoreductase (PFOR)–dependent electron transfer crucial for anaerobic energy metabolism in protozoa and anaerobic bacteria. In viruses, tizoxanide inhibits viral hemagglutinin maturation and blocks viral morphogenesis. These combined antiparasitic and antiviral actions make it effective across a broad spectrum of pathogens.

• Absorption: Well absorbed orally, enhanced with food.
• Distribution: Rapidly converted to tizoxanide; highly protein bound (>99.9%).
• Peak Plasma (Tmax): ~1–4 hours after dosing.
• Metabolism: Ester hydrolysis to tizoxanide; further glucuronidation in liver.
• Half‑Life: Tizoxanide ~1–1.5 hours.
• Elimination: Excreted as metabolites in urine (approx. 43%) and feces (35%).

• Pregnancy: No formal FDA category. Animal studies at high doses show no teratogenicity. Use only if potential benefit justifies potential risk.
• Lactation: Unknown if excreted into human milk; caution advised, especially in infants younger than 1 year.

• Primary Class: Antiprotozoal / Antidiarrheal
• Subclasses:
• Nitrothiazolyl-salicylamide derivative
• Broad-spectrum antiparasitic and antiviral

• Known hypersensitivity to nitazoxanide or any component of the formulation.

• May cause mild gastrointestinal upset—mild symptoms, such as abdominal pain or dyspepsia, resolve without intervention.
• Discolored urine (yellowish-orange tint) may occur; benign.
• Use with caution in pregnancy and lactation due to limited safety data.
• Monitor for allergic reactions during initial dosing.

Common (≥1%):

• Gastrointestinal: Abdominal pain, nausea, vomiting, anorexia, diarrhea.
• Laboratory: Transient mild elevations in AST/ALT.

Less Common / Rare:

• Headache, dizziness.
• Rash or urticaria (hypersensitivity).
• Rare serious liver enzyme elevations, usually mild and reversible.

Timing: GI side effects typically appear within days of starting therapy, often mild and self-limited.

• No significant interactions with CYP450 enzymes.
• Low risk of drug–drug interactions due to unique metabolism.
• No known food interactions beyond improved absorption with meals.
• No known alcohol interaction.

• Listed by WHO as essential medicine for parasitic diarrhea.
• Some regions support off-label use within treatment guidelines for H. pylori eradication regimens.
• Investigational antiviral use during COVID‑19 pandemic; current guidance permits only within clinical trials.
• Rare reports about hepatic enzyme elevations have prompted recommendations for checking liver function in long-course treatments beyond labeled use.

• Temperature: Store between 20 °C and 25 °C (68 °F to 77 °F); excursions permitted between 15 °C and 30 °C (59 °F to 86 °F).
• Humidity: Store in a dry place; protect oral suspension from moisture.
• Light: Shield from direct light.
• Handling: Shake suspension well before use; keep tablet bottles closed tightly.
• Reconstitution: No reconstitution needed beyond shaking.
• Do not freeze. Keep out of reach of children.