Mitoxantrone hydrochloride is primarily used in the treatment of certain types of cancer, including acute myeloid leukemia, non-Hodgkin's lymphoma, and breast cancer. It works by interfering with the DNA in cancer cells, preventing their growth and replication. Additionally, it is utilized in the management of multiple sclerosis, particularly for reducing the frequency of relapses and slowing disease progression in patients with worsening forms of the condition. The drug is administered intravenously under medical supervision due to its potent effects and potential side effects, which include cardiotoxicity and bone marrow suppression. Regular monitoring of heart function and blood counts is essential during treatment to mitigate risks.