Etoposide is a chemotherapy medication primarily used to treat various types of cancer, including testicular cancer and lung cancer. It works by inhibiting the enzyme topoisomerase II, which is essential for DNA replication. By disrupting this process, etoposide helps to prevent cancer cells from dividing and growing. Typically administered intravenously or in pill form, etoposide is often part of combination therapy with other anticancer drugs. Common side effects may include nausea, vomiting, hair loss, and an increased risk of infection due to its impact on the immune system. Regular monitoring is essential during treatment.