Hydroxychloroquine (Plaquenil)

Hydroxychloroquine (Plaquenil) is a medicine used to treat autoimmune diseases like lupus, rheumatoid arthritis (RA), and other inflammatory conditions. It is called a disease-modifying anti-rheumatic drug (DMARD), which means It can decrease the pain/swelling from arthritis and prevent joint damage. Hydroxychloroquine was first used to prevent and treat malaria but was later found to have benefits in autoimmune diseases. The mechanism of action of hydroxychloroquine is not clear, but it is thought to interfere with communication in the immune system. Hydroxychloroquine does not strongly suppress your immune system.

How to Take It

Hydroxychloroquine comes as a pill you take by mouth. Most adults take from 200 mg to 400 mg per day. It can be taken as a single daily dose or split into two doses. It is recommended to be taken with food to prevent stomach upset. Symptoms can improve in one to two months, but it can take up to six months for the full benefits of this medication.

Side Effects

Hydroxychloroquine typically is well tolerated. The most common side effects are nausea and diarrhea, which often improve with time. Other less common side effects include rash, hair thinning, and muscle weakness. Rarely, hydroxychloroquine can lead to low blood counts, typically in people with G6PD deficiency or porphyria.

In rare cases, hydroxychloroquine can affect the retina of the eye and cause visual changes or loss of vision. Such problems are more likely to occur in individuals taking high doses for many years, those 60 years or older, those with significant kidney or liver disease, and those with underlying retinal disease. At the recommended dose, the development of visual problems is rare. It is recommended that you have an eye exam within the first year of use, then repeat every 1 to 5 years, as advised by your eye doctor Make sure you tell your eye doctor you take hydroxycholorquine.

Very rarely, hydroxycholorquine has been linked to changes in the heart rhythm particularly in combination with other medications. This is uncommon and typically not a concern for most patients taking it as prescribed. Your doctor may recommend an EKG if you are on certain other medications including antidepressants, antibiotics, heart rhythm or anti-nausea medications.

Tell Your Rheumatology Provider

Although there are few drug interactions with hydroxychloroquine, be sure to tell your rheumatology provider about all medications you are taking, including over-the-counter drugs and natural remedies.

Be sure to notify your other providers when taking this drug. This drug is not known to suppress your immune system. Obtain vaccines recommended for healthcare maintenance after discussion with your primary care doctor. Notify your eye doctor when on this medication so regular visual screening tests can be performed. If you are pregnant, considering becoming pregnant, or lactating, please discuss with your rheumatology provider that you are taking this medication. Hydroxychloroquine has been shown to be safe during pregnancy and breastfeeding.

Updated January 2026 by Nina Couette, DO, and reviewed by the American College of Rheumatology Committee on Communications and Marketing.

This information is provided for general education only. Individuals should consult a qualified healthcare provider for professional medical advice, diagnosis, and treatment of a medical or health condition.