Is Niclosamide FDA approved?

Introduction to Niclosamide

Niclosamide may not be a household name, but it has drawn renewed interest in recent years due to its potential in treating more than just parasitic infections. From being a decades-old anti-tapeworm drug to possibly combating cancer and COVID-19, niclosamide is making headlines. But the big question remains—Is Niclosamide FDA-approved? Let’s explore the facts.

The current FDA status of niclosamide, its approved uses, and new investigational roles in cancer, COVID-19, and more.

History and Discovery

Niclosamide was first developed in the 1950s as an anthelmintic agent—a drug designed to expel parasitic worms. It has been widely used across the globe and even listed by the World Health Organization (WHO) as an essential medicine due to its importance in basic healthcare systems.

Classification and Use as an Anthelmintic

It belongs to a class of medications called salicylanilides, effective in treating tapeworm infections. It works without being absorbed into the bloodstream, making it both safe and effective for intestinal parasites.

How the FDA Approves Drugs?

The U.S. Food and Drug Administration (FDA) rigorously evaluates medications for safety, efficacy, and manufacturing quality before approving them. This includes preclinical studies, multiple phases of clinical trials, and an extensive review of labeling and documentation.

· Fast Track and Off-Label Use Explained

Some drugs may receive Emergency Use Authorization (EUA) or be used off-label, meaning they’re used for a condition not officially approved by the FDA. This distinction is crucial when discussing drugs like Niclosamide 500 mg that are being repurposed.

· Current FDA Status of Niclosamide

Yes, niclosamide is FDA-approved—but only for treating certain types of tapeworm infections. The drug was approved by the FDA in 1982 and marketed in the U.S. under the brand name Niclocide.

· Approved Medical Indications

It’s indicated for infections caused by:

Taenia saginata (beef tapeworm)
Taenia solium (pork tapeworm)
Diphyllobothrium latum (fish tapeworm)
Hymenolepis nana (dwarf tapeworm)

The FDA officially approves no other uses.

How Niclosamide Works?

Niclobest 500mg disrupts the energy metabolism of parasites by inhibiting oxidative phosphorylation, essentially depriving them of energy. This results in the paralysis and expulsion of the worm from the intestines.

· Targeted Parasites and Diseases

It’s peculiar to intestinal tapeworms and is not absorbed systemically, which limits its effectiveness against infections outside the digestive tract.

· Available Brands and Formulations

Niclosamide is available in chewable tablet form, typically 500 mg per tablet. It is taken orally and is prescription-only in the United States.

Dosage Guidelines

The usual dosage varies by age and weight, and is often administered as a single-day treatment. The recommended dose must be tailored by a oncologist.

Is Niclosamide Approved for COVID-19?

· Research and Clinical Trials

During the COVID-19 pandemic, niclosamide showed promise in laboratory studies due to its antiviral and anti-inflammatory properties. Several clinical trials were launched to investigate its effectiveness in treating SARS-CoV-2.

· Emergency Use and Limitations

However, niclosamide is not FDA-approved for COVID-19, nor has it received Emergency Use Authorization. Trials are ongoing, and results are still inconclusive as of mid-2025.

· Investigational Uses Beyond Parasites

· Cancer Treatment Potential

Recent research has found that niclosamide may inhibit cancer cell growth by targeting pathways like Wnt/β-catenin, Notch, and mTOR. Still, these findings are preliminary and not FDA-approved.

· Antiviral and Antibacterial Research

Niclosamide has shown activity against:

Zika virus
SARS-CoV
Multidrug-resistant bacteria like MRSA

These uses are investigational only and have not received regulatory approval.

What Experts Say About Repurposing Niclosamide?

· Opinions from Health Professionals

Experts applaud niclosamide’s low cost, safety profile, and versatility, but stress the importance of thorough trials before broadening its use.

· Statements from Regulatory Bodies

The FDA maintains that repurposed drugs must meet the same rigorous standards as new drugs, regardless of previous approval.

Differences Between Approval and Authorization

· Emergency Use Authorization (EUA) vs. Full Approval

EUA allows limited use in emergencies, while full approval requires extensive proof of safety and efficacy. Niclosamide has neither EUA nor full approval for any condition beyond tapeworm infections.

This means any use outside its original indication is technically off-label and subject to medical discretion.

Global Regulatory Status

· WHO and European Medicines Agency (EMA) Stance

The WHO includes niclosamide on its list of essential medicines. The EMA has also approved it for parasitic infections, but has not expanded its indications.

· Availability in Other Countries

Many developing nations use niclosamide regularly due to its affordability and effectiveness.

Side Effects

Most side effects are mild, including:

Nausea
Vomiting
Abdominal discomfort

As with any drug, adverse effects can be reported through the FDA’s MedWatch program.

Can Niclosamide Be Used Off-Label?

· Legal Considerations

Yes, physicians may prescribe niclosamide off-label, but this must be based on sound clinical judgment and patient consent.

· Physician Guidance and Risks

Patients should never self-medicate. Always consult a licensed doctor before considering any off-label use.

Challenges in Repurposing Older Drugs

· Economic and Clinical Hurdles

Old drugs like niclosamide may lack financial incentives for pharmaceutical companies to invest in new approvals, despite promising results.

· Industry Perspectives

Without the backing of large-scale sponsors, many such trials face delays or limited funding.

Availability of Niclosamide in the U.S.

· Prescription Requirements