Hydroxychloroquine, sold under the brand name Plaquenil, is a medication used to treat and prevent malaria caused by mosquito bites. It is also used to treat certain autoimmune diseases such as lupus and rheumatoid arthritis. Hydroxychloroquine belongs to a class of medications known as disease-modifying antirheumatic drugs (DMARDs) . It can decrease the pain and swelling of arthritis, which can prevent joint damage leading to long-term disability. Hydroxychloroquine can modify the underlying disease process, rather than simply treating the symptoms. It can reduce skin problems in lupus and prevent swelling/pain in arthritis. The dosage and length of treatment are based on the patients medical condition and response to treatment. It is important to take this medication exactly as directed by the doctor, and to not stop taking it without consulting the doctor first. Hydroxychloroquine is not recommended for coronavirus infection, also known as COVID-19, unless the patient is enrolled in a study.