Daunorubicin is a type of chemotherapy medicine called a cytotoxic anthracycline antibiotic. It is used to treat cancer of the blood (leukaemia). Cancers form when cells within the body multiply abnormally and uncontrollably. These cells spread, destroying nearby tissues. Daunorubicin works by stopping the cancer cells from multiplying. Its exact mechanism of action is unknown but it seems to work by inhibiting cell growth.Daunorubicin inserts itself into the strands of genetic material (DNA) inside the cancerous cells and binds them together. This prevents the cells from making genetic material (DNA and RNA) and proteins. This prevents the cells from growing and therefore they die. Unfortunately, daunorubicin can also affect normal, healthy cells, particularly those that multiply quickly, such as blood cells and hair cells. The most important side effect is on the bone marrow, where blood cells are made. Daunorubicin decreases the production of normal healthy blood cells, which can leave people susceptible to infection. Regular blood tests are needed to monitor the levels of blood cells. In most chemotherapy regimens, doses are administered in courses at various intervals to allow normal cells to recover from the adverse effects of the anticancer medicines between doses. However, during this period, cancer cells will also recover and start to replicate again. Successful treatment depends on the administration of the next course of therapy before the cancer has re-grown to its previous size and the net effect is to decrease the amount of cancer with each successive course. Daunorubicin is administered by injection or drip (infusion) into a vein.