Quinine dihydrochloride monohydrate is primarily used as an antimalarial medication, effective in treating malaria caused by Plasmodium falciparum, especially in cases where the parasite has developed resistance to other treatments. It works by interfering with the parasite's ability to digest hemoglobin, ultimately leading to its death. Beyond malaria, it is sometimes employed to manage nocturnal leg cramps, although this use is less common due to potential side effects. In laboratory settings, it serves as a key reference standard in pharmacological and biochemical research to study antimalarial compounds and their mechanisms of action. Additionally, its fluorescent properties make it useful in certain analytical chemistry applications, such as detecting and quantifying substances in solution.