Hydroxychloroquine is a prescription medication used primarily to treat autoimmune diseases like lupus and rheumatoid arthritis, and to prevent malaria in travelers. Originally developed as an antimalarial drug in the mid-20th century, it has become far more widely prescribed for conditions where the immune system attacks the body’s own tissues.
Lupus: The Most Common Use
Systemic lupus erythematosus, commonly called lupus, is the condition most closely associated with hydroxychloroquine. The drug is considered a cornerstone of lupus treatment, and most rheumatologists recommend it for nearly every lupus patient regardless of disease severity. It prevents disease flares, protects against irreversible organ damage, and reduces the risk of blood clots and bone loss.
The survival benefit is striking. In a large multiethnic U.S. study (the LUMINA cohort), only 5% of lupus patients taking hydroxychloroquine died during a median follow-up of about three years, compared with 17% of those not taking it. That protective effect held up even after researchers accounted for differences in disease severity and other factors that influence whether a doctor prescribes the drug in the first place. For patients with lupus-related kidney disease, hydroxychloroquine also improves the response to other immunosuppressive treatments.
Rheumatoid Arthritis
In rheumatoid arthritis, hydroxychloroquine is classified as a disease-modifying anti-rheumatic drug, meaning it doesn’t just mask pain but actually slows the underlying process that damages joints. It’s often prescribed alongside other medications in the same class, particularly for mild to moderate disease. Symptoms can start improving within one to two months, but the full benefit often takes up to six months to appear, so patience matters early on.
Malaria Prevention
Hydroxychloroquine and its close relative chloroquine were originally designed to fight malaria. Today, hydroxychloroquine is used to prevent malaria in travelers heading to regions where the parasite remains sensitive to the drug. You typically start taking it before travel, continue during your trip, and keep taking it for several weeks after returning. It is not effective in areas where the malaria parasite has developed resistance to chloroquine-based drugs, which includes large parts of sub-Saharan Africa and Southeast Asia. Your travel medicine provider can tell you whether it’s the right choice for your destination.
Other Autoimmune and Skin Conditions
Doctors also prescribe hydroxychloroquine off-label for a range of other conditions driven by immune system dysfunction. Sjögren’s syndrome, a condition that causes severe dryness in the eyes and mouth along with fatigue and joint pain, is one of the more common off-label uses, though clinical trial evidence for its effectiveness there is more limited than in lupus. It is also used for certain inflammatory skin conditions, including some forms of dermatitis and cutaneous lupus (lupus that primarily affects the skin).
How It Works in the Body
Hydroxychloroquine works by getting absorbed into small compartments inside cells called lysosomes, which act as the cell’s recycling centers. Once inside, the drug raises the pH of these compartments, making them less acidic. This disrupts several immune processes that depend on an acidic environment, effectively dialing down the overactive immune signaling that drives autoimmune diseases. In malaria, the same mechanism interferes with the parasite’s ability to survive inside red blood cells. The drug actually causes lysosomes to swell and multiply, which is part of why it accumulates in tissues over time and takes weeks to reach full effectiveness.
Dosing and What to Expect
The standard dose for most adults is 400 mg per day, taken as two 200-mg tablets. This dose is designed for people with a lean body weight above about 135 pounds. For those who weigh less, the dose is adjusted downward to 6.5 mg per kilogram of lean body weight. Getting the dose right matters because taking too much relative to your body size increases the risk of side effects, particularly eye damage over the long term.
Most people tolerate hydroxychloroquine well. The most common side effects are mild: nausea, stomach cramps, and occasional headaches, especially in the first few weeks. These often settle down as your body adjusts.
Eye Monitoring on Long-Term Use
The most significant long-term concern with hydroxychloroquine is retinal toxicity, a type of damage to the light-sensing layer at the back of the eye. This is uncommon in the first several years of use but becomes more likely the longer you take the drug. The American Academy of Ophthalmology recommends a baseline eye exam soon after starting therapy, including imaging of the retina. Annual screening can be deferred during the first five years if you don’t have significant risk factors. If risk factors are present, such as kidney disease, higher dosing, or pre-existing retinal problems, annual screening should start right away.
When caught early through routine screening, retinal changes are typically mild and can be managed by stopping the drug before vision is affected. This is why consistent follow-up matters, especially after the five-year mark.
Drug Interactions to Know About
Hydroxychloroquine can interact with several other medications. The most serious interactions involve drugs that also affect heart rhythm, because the combination can increase the risk of dangerous irregular heartbeats. Certain antipsychotic medications and heart rhythm drugs should not be taken with hydroxychloroquine at all.
It can also interact with diabetes medications by lowering blood sugar more than expected, which means people with diabetes may need closer monitoring of their glucose levels. Antacids can reduce how well hydroxychloroquine is absorbed, so they should be taken several hours apart. If you’re on methotrexate, cyclosporine, digoxin, or seizure medications, your doctor will likely want to monitor levels or adjust dosing.
The COVID-19 Chapter
Hydroxychloroquine gained enormous public attention in 2020 when it was proposed as a potential treatment for COVID-19. The FDA initially granted emergency authorization based on laboratory cell studies, not human trials. Within months, that authorization was revoked. Clinical trials showed hydroxychloroquine did not effectively treat COVID-19, did not prevent infection, and caused heart problems at a higher rate than expected. The FDA ended emergency use in June 2020, and no major medical organization currently recommends it for COVID-19 prevention or treatment.
For the millions of people who take hydroxychloroquine for lupus, rheumatoid arthritis, and other autoimmune conditions, the drug remains a well-established and effective therapy with decades of clinical use supporting its benefits.