Nitazoxanide Syrup (Oral Suspension)

Brand name: Alinia Formulation: 100 mg / 5 mL oral suspension (powder for reconstitution - add 48 mL water to make final suspension) Drug class: 5-nitrothiazole antiprotozoal / broad-spectrum antiparasitic

Drug Description

Nitazoxanide is a synthetic, oral nitrothiazolyl-salicylamide prodrug with broad-spectrum activity against intestinal protozoa and helminths. The syrup formulation is specifically intended for children aged 1-11 years, as the 500 mg tablet contains more drug than the pediatric dose requires.

Katzung's Basic and Clinical Pharmacology, 16th Ed, p. 1454
Goodman & Gilman's The Pharmacological Basis of Therapeutics

Mechanism of Action

Nitazoxanide interferes with the pyruvate:ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reaction, which is essential to anaerobic energy metabolism in protozoan and bacterial species. The PFOR enzyme of Giardia lamblia directly reduces nitazoxanide by electron transfer. A similar PFOR sequence is found in Cryptosporidium parvum. This mechanism may not be the only pathway involved.

Unlike metronidazole, nitazoxanide and its metabolites are free of mutagenic effects.

Harrison's Principles of Internal Medicine 22E (2025)
Goodman & Gilman's

Pharmacokinetics (ADME)

Parameter	Detail
Absorption	Rapid after oral administration; improved with food
Prodrug conversion	Rapidly hydrolyzed to active metabolite tioxanide (desacetyl-nitazoxanide)
Further metabolism	Tioxanide undergoes glucuronidation → tioxanide glucuronide
Protein binding	>99.9% (plasma protein bound)
Tmax	1-4 hours after dosing
Excretion	Tioxanide: urine, bile, feces; Tioxanide glucuronide: urine and bile
Renal/hepatic impairment	Not formally studied; use with caution

Drug interaction caution: Due to >99.9% plasma protein binding, nitazoxanide may compete with other highly protein-bound drugs that have a narrow therapeutic index.

Indications (Approved)

Giardiasis (Giardia lamblia / G. intestinalis) - efficacy 85-90%
Cryptosporidiosis (Cryptosporidium parvum) - efficacy 56-88% in immunocompetent patients

Limitation: NOT effective for diarrhea caused by C. parvum in HIV-infected or immunodeficient patients (FDA label). Immunocompromised patients may require extended therapy (2 weeks or longer).

Off-Label / Extended Spectrum Uses

Nitazoxanide has shown efficacy against a wide range of organisms:

Entamoeba histolytica (amebiasis)
Blastocystis hominis
Cyclospora cayetanensis
Isospora belli
Trichomonas vaginalis
Hymenolepis nana, Trichuris trichiura, Ascaris lumbricoides, Enterobius vermicularis (helminths)
Fasciola hepatica
Helicobacter pylori (as part of quadruple therapy)
Metronidazole-resistant protozoal strains

Dosage - Syrup (100 mg/5 mL)

Age Group	Dose	Frequency	Duration
1-3 years	5 mL (100 mg)	Every 12 hours	3 days
4-11 years	10 mL (200 mg)	Every 12 hours	3 days
<1 year	Not established	-	-
≥12 years	Switch to 500 mg tablet	Every 12 hours	3 days

Always administer with food.

For immunocompromised patients with cryptosporidiosis: extend therapy to 2 weeks or longer (and optimize antiretroviral therapy if HIV-positive).

Suspension Preparation

Tap bottle until all powder flows freely
Add approximately half of 48 mL water first and shake vigorously
Add remaining water and shake again
Final volume makes a 100 mg/5 mL suspension
Keep refrigerated; shake well before each use

Adverse Effects

Nitazoxanide is generally well tolerated. Adverse effects are uncommon and usually mild:

Abdominal pain
Diarrhea
Nausea / vomiting
Headache
Greenish tint to urine (benign, due to drug metabolites)

Note: these adverse event rates are comparable to placebo in trials.

Contraindications

Hypersensitivity to nitazoxanide or any component of the formulation
Tablets (500 mg) must not be used in children ≤11 years (dose mismatch; use oral suspension instead)

Safety in Special Populations

Population	Notes
Pregnancy	Former FDA Category B; no teratogenicity in animal studies; no human data
Lactation	Caution advised; data limited
HIV/Immunocompromised	Reduced efficacy for cryptosporidiosis; extended courses needed
Hepatic impairment	Not studied; use with caution
Renal impairment	Not studied; use with caution

Key Distinguishing Features

Broad spectrum - single agent can treat mixed intestinal infections (protozoa + helminths)
Active against metronidazole-resistant Giardia
Not mutagenic (unlike metronidazole/tinidazole)
Short 3-day treatment course
Pediatric-friendly syrup formulation (age 1-11)

Sources: Goodman & Gilman's Pharmacological Basis of Therapeutics; Harrison's Principles of Internal Medicine 22E (2025); Katzung's Basic and Clinical Pharmacology 16th Ed; FDA Prescribing Information (Alinia)

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