Nitazoxanide Drug Interactions: What to Avoid and What to Tell Your Doctor

Nitazoxanide (brand name Alinia) has a relatively limited drug interaction profile compared to many antibiotics. It does not significantly inhibit cytochrome P450 enzymes — the metabolic pathway responsible for most antibiotic-drug interactions. However, its active metabolite tizoxanide is extraordinarily protein-bound (more than 99.9% bound to plasma proteins), which creates an important and unique class of drug interactions.

The Main Interaction Mechanism: Protein Binding Competition

Many drugs travel through the bloodstream bound to plasma proteins (primarily albumin). Protein-bound drug is "inactive" — it's the free, unbound fraction that produces the therapeutic effect. When two highly protein-bound drugs are taken together, they compete for the same binding sites. If tizoxanide displaces another drug from its protein binding, more of that other drug becomes "free" in the bloodstream — potentially increasing its levels and effects (or toxicity).

This is especially significant for drugs with narrow therapeutic indices (NTIs) — medications where a small change in blood level can mean the difference between therapeutic effect and toxicity.

Warfarin (Coumadin) — Avoid Concurrent Use

Warfarin is the most important drug interaction to be aware of with nitazoxanide. The prescribing information specifically states to avoid concurrent warfarin use. Warfarin is itself highly protein-bound, and competition between tizoxanide and warfarin for binding sites can lead to elevated free warfarin levels — increasing the risk of bleeding.

If you are on warfarin and need to take nitazoxanide, discuss this with your prescriber. An alternative antiparasitic (such as metronidazole or tinidazole for Giardia) may be preferable. If concurrent use is unavoidable, close INR monitoring is essential.

Phenytoin (Dilantin) — Avoid or Use Alternative

Phenytoin, an anti-seizure medication, is highly protein-bound and has a narrow therapeutic index. Co-administration with nitazoxanide is classified as a "Serious — Use Alternative" interaction, with the potential for either drug to increase the levels of the other via protein binding competition. If you take phenytoin, notify your doctor before starting nitazoxanide.

Baricitinib (Olumiant) — Avoid Concurrent Use

Nitazoxanide inhibits the organic anion transporter 3 (OAT3) pathway, which is responsible for eliminating baricitinib (a JAK inhibitor used for rheumatoid arthritis and other inflammatory conditions). Blocking OAT3 increases baricitinib levels in the blood. Co-administration is not recommended — use an alternative antiparasitic if baricitinib therapy is ongoing.

Valproic Acid (Depakote) — Use Alternative

Valproic acid (used for epilepsy and bipolar disorder) is another highly protein-bound drug that competes with tizoxanide. This interaction is classified as "Avoid or Use Alternative." If you are taking valproic acid, tell your prescriber — they may need to select a different antiparasitic or monitor valproate levels carefully.

Monitor Closely: Other Protein-Bound Drugs

The following drugs are also highly protein-bound and warrant close monitoring if used concurrently with nitazoxanide, though interactions are generally moderate rather than severe:

• Glyburide (a diabetes medication)
• Tacrolimus (an immunosuppressant)
• Cisplatin (chemotherapy)
• Chlorthalidone and bumetanide (diuretics)
• Aspirin at higher doses
• Clindamycin

What Nitazoxanide Does NOT Significantly Interact With

Unlike metronidazole, nitazoxanide does NOT have a significant interaction with alcohol. There is no disulfiram-like reaction, no nausea or vomiting triggered by alcohol consumption, and no alcohol restriction in the prescribing information. This is a meaningful advantage for patients who have had problems with metronidazole's alcohol requirement.

Also unlike many antibiotics, nitazoxanide does not significantly inhibit cytochrome P450 enzymes (specifically CYP3A4, CYP2D6, etc.) — so it does not affect the metabolism of the large number of drugs that use these pathways.

What to Tell Your Doctor and Pharmacist

Before starting nitazoxanide, tell your prescriber and pharmacist about all medications you take, including:

• Blood thinners, especially warfarin (Coumadin, Jantoven)
• Anti-seizure medications, especially phenytoin or valproic acid
• Immunosuppressants (tacrolimus, cyclosporine)
• JAK inhibitors such as baricitinib (Olumiant)
• Any diabetes medications
• All herbal supplements and over-the-counter medications

For more on what to expect from nitazoxanide treatment, see our companion guide: Nitazoxanide Side Effects: What to Expect

Once you have your prescription, medfinder can locate pharmacies near you with nitazoxanide in stock.