Chapter 35: Anticancer Chemotherapy Drugs

A critical distinction is made between cell cycle-nonspecific (CCNS) drugs, which act during any phase including the resting G0 phase, and cell cycle-specific (CCS) agents, which target rapidly dividing cells during specific phases like DNA synthesis or mitosis. The text elaborates on the rationale for combination chemotherapy to maximize tumoricidal effects, delay drug resistance, and manage toxicity through distinct mechanisms of action. Significant attention is dedicated to the general adverse effects of cytotoxic therapy, particularly myelosuppression, which results in anemia, leukopenia, and thrombocytopenia, requiring careful monitoring of the nadir period. The chapter systematically categorizes major drug classes: alkylating agents like cyclophosphamide that cross-link DNA to prevent replication, often requiring hydration to prevent hemorrhagic cystitis; antimetabolites such as methotrexate and fluorouracil (5-FU) that disrupt metabolic pathways and DNA synthesis during the S-phase; and antitumor antibiotics like doxorubicin, known for their ability to inhibit DNA and RNA transcription and the risk of cumulative cardiotoxicity. Furthermore, the summary covers plant alkaloids, including vinca alkaloids (vincristine) and taxanes, which arrest mitosis by interfering with microtubule function and are associated with neurotoxicity. The chapter concludes by reviewing hormonal agents like tamoxifen and aromatase inhibitors used to modulate hormone-dependent tumors, alongside emerging immunomodulators and vaccines designed to stimulate the immune system against malignancies.