Plaquenil is a type of medication classified as an antimalarial drug. Plaquenil is listed by the WHO as one of the most important medications needed for basic health. Plaquenil is listed among a group of drugs known as disease modifying anti-rheumatic drugs or DMARDS. Plaquenil is used to treat malaria caused by mosquito bites. However, it is not very effective against chloroquine-resistant malaria. Plaquenil is prescribed for treatment of autoimmune diseases. It works by interfering with the communication of cells within the immune system.