Hydroxychloroquine is used to treat rheumatoid arthritis, juvenile chronic arthritis, discoidal, and systemic lupus erythematosus, and may also be useful in the relief of skin lesions triggered or exacerbated by sunlight. The mechanism of action of this drug is not clear, but may be related to stabilization of lysosomal membranes, inhibition of prostaglandin formation, inhibition of polymorphonuclear cell chemotaxis and phagocytosis, possible interference with the formation of monocyte interleukin 1, and inhibition of the release of superoxide from neutrophils.