Hydroxychloroquine is in a class of drugs called antimalarials and is also an antirheumatic drug. It works by killing the organisms that cause malaria. Hydroxychloroquine work to treat rheumatoid arthritis and systemic lupus erythematosus by decreasing the activity of the immune system. Hydroxychloroquine is a disease-modifying anti-rheumatic drug (DMARD). It works by calming your immune system. This helps reduce swelling (inflammation) in people with autoimmune conditions, where your immune system attacks your own body.