Chloroquine: Uses, Side Effects, Dosage & the Latest COVID‑19 Findings

• by Simon Bruce
• Sep, 21 2025

TL;DR:

• Chloroquine is an old antimalarial drug now also used for some autoimmune conditions.
• It works by raising the pH inside parasite‑infected cells, stopping the parasite from growing.
• Common side effects include nausea, headache and retinal toxicity with long‑term use.
• Standard malaria dose: 600mg on day1, then 300mg on days2‑3; dosage differs for rheumatoid arthritis.
• COVID‑19 studies show no clear benefit; major health agencies advise against routine use.

What Is Chloroquine and How Does It Work?

Chloroquine is a synthetic compound first synthesized in the 1930s. It gained fame as a cheap, effective treatment for Plasmodium malaria, especially the strains that were still sensitive to the drug in the 1950s. Over time, doctors discovered it also dampens the immune system, so it earned a second life treating autoimmune diseases like lupus and rheumatoid arthritis.

The magic lies in chemistry: chloroquine is a weak base that piles up in acidic organelles-think lysosomes and the parasite’s food vacuole. By raising the pH, it messes up the parasite’s ability to digest hemoglobin, essentially starving it. In autoimmune conditions, the same pH shift interferes with antigen presentation, reducing inflammation.

"Chloroquine’s dual action-antiparasitic and immunomodulatory-makes it a unique tool in the pharmacological toolbox," notes Dr. Margaret Chan, former WHO Director‑General.

Because the drug accumulates in tissues, especially the retina, clinicians monitor patients closely for eye toxicity.

Approved Uses: From Malaria to Autoimmune Disorders

In 2025, chloroquine is officially approved for two main indications:

• Uncomplicated malaria caused by chloroquine‑sensitive P. vivax and P. ovale.
• Rheumatoid arthritis and systemic lupus erythematosus where it serves as a steroid‑sparing agent.

Off‑label, it sometimes appears in dermatology for severe psoriasis and in certain viral research labs, but those uses lack robust regulatory backing.

For malaria, the World Health Organization (WHO) still lists chloroquine as a first‑line drug only in regions where resistance is absent-namely parts of Central America and Oceania. In Australia, chloroquine is stocked in most hospital pharmacies for travelers returning from endemic zones.

Dosage Guidelines and Administration Tips

Getting the dose right is crucial. Below is a quick‑reference table for the most common regimens.

Tips to minimise side effects:

1. Take the tablet with food or a full glass of water to reduce stomach upset.
2. Never crush or chew extended‑release forms; they’re designed for slow release.
3. Schedule a baseline ophthalmology exam before starting long‑term therapy, then annually.
4. Stay hydrated-chloroquine can cause mild diuresis.

If you miss a dose, take it as soon as you remember unless it’s within 12hours of the next scheduled dose; then skip and continue as normal.

Safety Profile: Side Effects, Interactions & the COVID‑19 Controversy

Like any drug, chloroquine isn’t risk‑free. Here’s what patients most often report:

Major drug interactions include:

• Antacids (reduce absorption).
• QT‑prolonging agents like azithromycin, hydroxychloroquine, certain anti‑psychotics.
• Cytochrome P450 inhibitors (e.g., erythromycin) can raise plasma levels.

Because of its effect on the heart rhythm, clinicians avoid prescribing chloroquine to patients with known arrhythmias or those on multiple QT‑prolonging meds.

COVID‑19: What the Science Says (2025 Update)

Early 2020 hype made headlines when a small French study suggested chloroquine might cut viral load. That spurred a global scramble, but larger, well‑controlled trials quickly knocked the hype down.

Key findings up to 2025:

• The RECOVERY trial (UK) enrolled >10,000 hospitalised patients and found no mortality benefit.
• The WHO SOLIDARITY trial halted the chloroquine arm early due to lack of efficacy and safety concerns.
• Meta‑analyses published in The Lancet and JAMA conclude that routine chloroquine or hydroxychloroquine use for COVID‑19 is not recommended.

Both the WHO and the U.S. CDC now list chloroquine as “not recommended for COVID‑19 treatment outside clinical trials.” In Australia, the Therapeutic Goods Administration (TGA) issued a reminder in March2024 that prescribing chloroquine for COVID‑19 without trial enrolment may expose patients to unnecessary risk.

Bottom line: if you’re looking for a COVID‑19 cure, chloroquine isn’t it. Stick to approved antivirals and supportive care.

Frequently Asked Questions

• Can I take chloroquine with alcohol? Small amounts won’t change the drug’s action, but heavy drinking can worsen liver toxicity.
• Is chloroquine safe in pregnancy? It’s classified as Category C in Australia - only use if benefits outweigh risks, typically under specialist supervision.
• Why do I need an eye exam? Long‑term accumulation in the retina can cause irreversible vision loss; early detection makes a huge difference.
• Is hydroxychloroquine the same? Hydroxychloroquine is a newer analogue with a slightly better safety profile, especially for eye toxicity, but it works the same way.
• Can I store chloroquine at home? Keep it in a cool, dry place, out of reach of children, and never use after the expiry date printed on the label.

Next Steps & Troubleshooting

If you’re starting chloroquine for malaria prophylaxis before a trip:

1. Consult your GP 1‑2weeks before departure.
2. Get baseline liver function tests.
3. Follow the dose schedule (usually 300mg weekly).
4. Carry a copy of the prescription in case you need refills abroad.

For chronic users (lupus or arthritis) who develop visual changes:

• Stop the drug immediately.
• Book an urgent ophthalmology appointment.
• Discuss alternative disease‑modifying agents with your rheumatologist.

Experiencing severe nausea or heart palpitations? Call your doctor right away; dose adjustment or a switch to hydroxychloroquine might be needed.

Remember, any medication works best when you pair it with regular monitoring and open communication with your healthcare team.