Chloroquine: What It Is, How It’s Used, and Why It’s Controversial

Chloroquine is a drug that was once a miracle medicine for malaria. For decades, it saved millions of lives across Africa, Asia, and South America. But today, it’s more famous for the hype, the controversy, and the misinformation than for its real medical use. If you’ve heard of chloroquine in the last five years, it’s probably because of the pandemic. But that’s not where its story begins-or ends.

What chloroquine actually is

Chloroquine is a synthetic compound developed in the 1930s by German scientists. It belongs to a class of drugs called 4-aminoquinolines. By the 1940s, it became the go-to treatment for malaria, especially the most common type caused by Plasmodium vivax and Plasmodium falciparum. It worked by killing the parasite inside red blood cells. For over 50 years, it was cheap, effective, and widely available.

It wasn’t just for malaria. Doctors also used it to treat autoimmune diseases like lupus and rheumatoid arthritis. Its anti-inflammatory properties made it useful for calming overactive immune responses. In some countries, it’s still prescribed for these conditions today.

Chloroquine’s chemical cousin, hydroxychloroquine, is slightly less toxic and became more popular for long-term autoimmune use. But both drugs work similarly and share the same risks.

Why it stopped working for malaria

By the 1990s, something changed. In Southeast Asia, then Africa, malaria parasites started resisting chloroquine. Scientists found mutations in the PfCRT gene that let the parasite pump the drug out of its cells before it could kill them. By 2006, the World Health Organization stopped recommending chloroquine as a first-line treatment for P. falciparum malaria in most of the world.

Today, artemisinin-based combination therapies (ACTs) are the standard. They work faster and still kill resistant strains. Chloroquine is only used in rare cases where the local parasite strain is still sensitive-like in parts of Central America or the Middle East.

That’s the reality: chloroquine is no longer the frontline weapon against malaria. It’s a backup, not a breakthrough.

The COVID-19 hype and why it backfired

In March 2020, chloroquine and hydroxychloroquine exploded into headlines. A small, poorly designed study in France suggested they might reduce viral load in COVID-19 patients. Within days, world leaders mentioned them on TV. Stockpiles emptied. People bought them online for prevention.

The problem? That study had 36 patients. No control group. No randomization. It was a case report, not science.

Over the next year, dozens of large, peer-reviewed studies came out. The RECOVERY trial in the UK, involving over 11,000 patients, found no benefit. The WHO’s Solidarity Trial showed no reduction in deaths. The U.S. FDA revoked its emergency use authorization in June 2020.

Worse, these drugs caused real harm. They can trigger dangerous heart rhythm problems-especially when combined with azithromycin, which was often prescribed alongside them. There were reports of patients needing pacemakers. Some died.

By late 2021, every major health agency agreed: chloroquine doesn’t work for COVID-19. Not for prevention. Not for treatment. Not even in early infection.

The real risks of chloroquine

Even when used correctly, chloroquine isn’t safe. It has a narrow therapeutic window-meaning the difference between a helpful dose and a toxic one is small.

Common side effects include:

• Nausea, vomiting, diarrhea
• Headaches and dizziness
• Blurred vision (which can become permanent)
• Low blood sugar
• Skin rashes

Long-term use, especially for lupus, can damage the retina. That’s why patients on chloroquine for more than five years need annual eye exams. The damage is often irreversible.

Heart risks are the most dangerous. Chloroquine can prolong the QT interval on an ECG, leading to torsades de pointes-a life-threatening arrhythmia. People with existing heart conditions, kidney disease, or those taking other QT-prolonging drugs are at highest risk.

Overdose is deadly. As little as 1 gram can be fatal in children. That’s why pharmacies in the UK and U.S. now limit how much can be sold at once.

Who still uses chloroquine today?

Despite the controversy, chloroquine hasn’t disappeared. It’s still prescribed in a few specific cases:

• Patients with lupus or rheumatoid arthritis who don’t respond to other drugs
• Malaria in regions where resistance hasn’t spread (like parts of Central America)
• Off-label use for certain skin conditions like porphyria cutanea tarda

In these cases, it’s used under strict supervision. Blood tests, ECGs, and eye checks are routine. Doctors don’t hand it out like vitamins.

It’s also used in research labs. Scientists study chloroquine’s mechanism to understand how parasites evade drugs-and how to design better ones.

What you should know if you’re considering chloroquine

If you’re thinking about taking chloroquine for any reason-whether for malaria, COVID, or something else-here’s what matters:

1. Don’t self-medicate. Never buy it online without a prescription.
2. It’s not a preventive. Taking it before exposure to malaria or COVID won’t protect you.
3. It’s not safe for everyone. If you have heart problems, liver disease, or G6PD deficiency, avoid it.
4. Eye damage is silent. You won’t feel it until it’s too late. Regular screenings are non-negotiable.
5. There are better options. For malaria, use WHO-approved ACTs. For lupus, there are newer, safer immunosuppressants.

Chloroquine isn’t evil. It saved lives. But it’s not a miracle drug. It’s a tool-powerful, risky, and only useful in the right hands, for the right conditions.

Where does chloroquine stand now?

Today, chloroquine is a cautionary tale. It shows how hope can outpace evidence. How a cheap, old drug can become a political symbol. How misinformation spreads faster than viruses.

It’s still in the WHO’s List of Essential Medicines-not because it’s widely used, but because it’s still needed in some places. It’s listed under "antimalarials," not "antivirals." That’s the truth.

Science didn’t abandon chloroquine because it was old. It abandoned it because better tools came along. And because people tried to use it for things it wasn’t meant for.

The lesson? Don’t romanticize old drugs. Don’t chase viral trends. Trust the data-not the headlines.