Cancer chemotherapeutic agents are drugs used to destroy cancer cells or stop their growth. These drugs mainly target rapidly dividing cells—one of the main characteristics of cancer. Chemotherapy may be used alone or in combination with surgery, radiation, targeted therapy, or immunotherapy depending on the cancer type and stage.
General Principles of Chemotherapy
- Selective toxicity: Drugs aim to damage cancer cells more than normal cells.
- Cell cycle effects: Some drugs work in specific stages of cell division, while others act on all proliferating cells.
- Combination therapy: Using multiple drugs with different mechanisms reduces drug resistance and improves outcomes.
- Dose scheduling: Chemotherapy is given in cycles to allow recovery of healthy tissues.
Classification of Cancer Chemotherapeutic Agents
1. Alkylating Agents
Damage DNA and prevent cancer cells from dividing.
- Cyclophosphamide
- Melphalan
- Cisplatin
2. Antimetabolites
Interfere with DNA and RNA synthesis by mimicking natural molecules.
- Methotrexate
- 5-Fluorouracil (5-FU)
- Cytarabine
3. Plant Alkaloids (Mitotic Inhibitors)
Block cell division during mitosis.
- Vincristine
- Vinblastine
- Paclitaxel
4. Antibiotic Anticancer Agents
Interfere with DNA replication and repair.
- Doxorubicin
- Bleomycin
5. Hormones and Hormone Antagonists
Used in hormone-dependent cancers such as breast and prostate cancer.
- Tamoxifen
- Letrozole
- Flutamide
6. Targeted Therapy
Acts on specific molecular targets involved in cancer growth.
- Imatinib
- Trastuzumab
7. Immunotherapy
Stimulates the immune system to attack cancer cells.
- PD-1 inhibitors
- CAR-T cell therapy
Mechanisms of Action
Chemotherapeutic agents work through various mechanisms such as:
- Damaging DNA structure
- Blocking DNA synthesis
- Stopping cell division during mitosis
- Blocking hormone receptors
- Inhibiting growth factor pathways
Pharmacokinetics
- Most drugs are given intravenously due to poor oral absorption.
- Dose adjustment is required in renal or liver impairment.
- They distribute widely and may accumulate in tissues.
Adverse Effects of Chemotherapeutic Agents
Chemotherapy affects both cancer cells and normal rapidly dividing cells. Common toxicities include:
- Bone marrow suppression (anemia, low WBC, low platelets)
- Hair loss
- Nausea and vomiting
- Diarrhea or constipation
- Mouth ulcers
- Organ-specific toxicity (kidney, heart, lungs)
Drug Resistance
Cancer cells may develop resistance due to:
- Decreased drug uptake
- Increased drug efflux (P-glycoprotein activity)
- Mutation of drug targets
- Enhanced DNA repair mechanisms
Role of Combination Chemotherapy
- Improves cancer cell kill rate
- Minimizes drug resistance
- Allows use of lower doses of each drug (reducing toxicity)
- Targets cancer cells at different stages
Patient Counseling
- Explain possible side effects like nausea, fatigue, and infections.
- Advise patients to avoid crowded places due to low immunity.
- Stress importance of attending scheduled cycles.
- Encourage healthy diet and proper hydration.
- Report fever, bleeding, or severe vomiting immediately.
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