Used primarily as an antiparasitic agent, quinacrine dihydrochloride dihydrate effectively treats infections caused by protozoa, such as malaria (by inhibiting Plasmodium growth in red blood cells), giardiasis, blackwater fever, and amebic dysentery. It also exhibits anti-inflammatory properties, making it useful in managing autoimmune conditions like lupus erythematosus. In research, it serves as a fluorescent stain for identifying nucleic acids in cellular studies and chromosome banding (Q-banding). Additionally, it has been explored for its potential anticancer properties in experimental treatments and as an aid in gastrointestinal diagnostics, such as detecting ulcers via fluorescence. Use under medical supervision due to potential severe side effects.