Chloroquine phosphate and hydroxychloroquine sulfate are substituted 4-amino quinoline compounds that differ only by a hydroxy group. Quinacrine hydrochloride also has the 4-amino quinoline radical but has, in addition, a benzene ring; it is classified as an acridine compound. The 4-amino quinoline radical is present in all antimalarial compounds shown to be effective in the treatment of lupus erythematosus (LE) (Figure).1HISTORYQuinacrine was introduced for malaria therapy in 1930. Its superiority over quinine was established during World War II, when it became the official drug for the treatment of malaria. The toxicity of quinacrine and its inability either to cure malaria or to act as an effective prophylactic, however, spurred continued research for better drugs. A large series of 4-amino quinolines were investigated. Of these, chloroquine proved to be the most promising and was released for field trial.2By the end of World War II, it had