Hydroxychloroquine sulfate is a colorless crystalline solid, which is soluble in water to at least 20 percent. The molecular weight of the drug is 335.872 g/mol and empirical formula C18H26ClN3O. It is sold under the brand name Plaquenil, which comes in tablets with 200 mg hydroxychloroquine sulfate. The route of administration is oral. The exact mechanism by which hydroxychloroquine treats or prevents malaria is not known. It is presumed that the drug exerts its effect by concentrating on the acid vesicles of the parasite and inhibiting certain enzymes.