Hydroxychloroquine

Key facts

• Hydroxychloroquine (sold as Plaquenil, among other brands) calms an overactive immune response and also kills the malaria parasite.
• For autoimmune disease it's taken daily, and the full effect can take weeks to months to appear.
• Long-term use can cause irreversible retinal damage. Regular eye exams (a baseline test, then yearly after five years of use) are required to catch changes early.
• It can also prolong the heart's QT interval. Seek urgent care for palpitations, fainting, or sudden vision changes.

What hydroxychloroquine treats

Hydroxychloroquine treats rheumatoid arthritis and systemic and cutaneous lupus erythematosus, reducing joint pain, skin lesions, and fatigue over weeks to months. It also prevents and treats malaria caused by susceptible parasite strains.

How hydroxychloroquine works

In autoimmune disease, hydroxychloroquine interferes with immune-cell signaling and antigen processing, dampening the inflammatory response over time. Against malaria, it concentrates inside the parasite and blocks its ability to process a byproduct of red blood cell digestion, killing the parasite as it feeds.

Before you take it

• Tell your prescriber about any existing retinal or macular disease, since hydroxychloroquine can add to that damage.
• Mention any heart rhythm problems, other medicines that prolong the QT interval, G6PD deficiency, or liver, kidney, or psoriasis history.
• You'll need a baseline eye exam before starting, and ongoing eye checks throughout treatment.
• Take it with food to reduce stomach upset, and don't stop long-term autoimmune treatment abruptly without medical advice, since symptoms can flare.

Side effects

Common effects include nausea, stomach upset, headache, and mild rash, usually easing as your body adjusts.

Stop and seek urgent medical care for any of these:

• Blurred vision, blind spots, or difficulty seeing at night.
• Palpitations, an irregular heartbeat, or fainting.
• Severe skin reactions such as blistering or peeling.
• Unusual muscle weakness.

Safety essentials

• Retinal toxicity is cumulative and can be permanent if missed. Attend every scheduled eye exam, and report any vision change immediately rather than waiting for your next appointment.
• Hydroxychloroquine can prolong the QT interval; tell every prescriber about other QT-prolonging medicines you take, and report palpitations or fainting straight away.
• Have periodic blood counts and muscle strength checked during long-term use, and don't take more than your prescribed dose; overdose can be dangerous.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.