epirubicin + pirarubicin + hydroxycamptothecin + fluorouracil

This is a **combination chemotherapy regimen** that includes four cytotoxic agents: **epirubicin**, **pirarubicin**, **hydroxycamptothecin**, and **fluorouracil**. Each drug has a distinct but complementary mechanism of action, aiming to maximize antitumor efficacy through additive or synergistic effects and minimize resistance development. - **Epirubicin** and **pirarubicin** are anthracycline antibiotics, primarily acting as topoisomerase II inhibitors. They intercalate into DNA, inhibit DNA and RNA synthesis, and generate free radicals causing DNA damage, leading to apoptosis of cancer cells[1][5][7][9]. - **Hydroxycamptothecin** is a camptothecin analog and functions as a topoisomerase I inhibitor, preventing religation of DNA single-strand breaks and resulting in DNA damage and cell death (not directly detailed in search but established mechanism). - **Fluorouracil** is an antimetabolite of the pyrimidine analog class, inhibiting thymidylate synthase and interfering with DNA synthesis, thereby blocking cell proliferation[2][4][6][10]. This combination is intended for use in multiple solid tumors, with individual components commonly used for **breast, gastric, colorectal, and other cancers**. Each component is an **intravenous chemotherapeutic**, most frequently administered in hospital or clinic settings under close supervision.