Chemotherapeutic Agents

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Introduction

Chemotherapy agents are drugs designed to target and destroy rapidly dividing cancer cells. By disrupting cell division, chemotherapy can control, reduce, or eliminate cancerous growths. However, because chemotherapy affects both cancerous and normal cells, particularly those that also rapidly divide (like hair follicles and bone marrow), it is associated with a range of side effects.

Mechanism of Action

• Chemotherapy agents target different stages of the cell cycle to prevent cancer cell replication.
• They work by interfering with DNA, RNA, or proteins essential for cell division, leading to cell death.
• Some agents are specific to certain phases of the cell cycle, while others act broadly on dividing cells.

Uses of Chemotherapy Agents

• Solid Tumours: Chemotherapy is commonly used in cancers such as breast, lung, colon, and ovarian cancers to shrink tumours, kill remaining cells after surgery, or control disease spread.
• Hematologic Malignancies: Blood cancers like leukaemia, lymphoma, and multiple myeloma are often treated with chemotherapy to target cancer cells circulating in the blood or bone marrow.
• Combination Therapy: Chemotherapy is often combined with surgery, radiation therapy, or immunotherapy to increase the overall effectiveness of cancer treatment.
• Palliative Care: In advanced cancers, chemotherapy may be used to relieve symptoms, reduce tumour size, and improve quality of life.

Classifications of Chemotherapy Agents

• Alkylating Agents: These work by binding to DNA and preventing cell division. Examples include cyclophosphamide and cisplatin.
• Antimetabolites: These mimic natural substances in the cell, disrupting DNA and RNA synthesis. Examples include methotrexate and 5-fluorouracil (5-FU).
• Antitumour Antibiotics: Derived from natural sources, these interfere with DNA function. Examples include doxorubicin and bleomycin.
• Topoisomerase Inhibitors: These interfere with enzymes that help in DNA replication. Examples include irinotecan and etoposide.
• Mitotic Inhibitors: These inhibit mitosis (cell division) by affecting microtubules. Examples include paclitaxel and vincristine.

Side Effects

• Bone Marrow Suppression: Many chemotherapy agents reduce the production of blood cells, leading to anaemia, increased risk of infections, and bleeding.
• Gastrointestinal Issues: Nausea, vomiting, diarrhoea, and mucositis (inflammation of the digestive tract) are common due to effects on rapidly dividing cells in the GI tract.
• Hair Loss (Alopecia): Chemotherapy often affects hair follicles, leading to temporary hair loss.
• Fatigue: A frequent side effect caused by anaemia, general weakness, or the body’s response to cancer treatment.
• Neuropathy: Some drugs cause peripheral neuropathy, leading to numbness or tingling in the hands and feet.
• Organ Toxicity: Certain agents are toxic to organs such as the heart (e.g., doxorubicin), kidneys (e.g., cisplatin), and lungs (e.g., bleomycin).

Monitoring and Precautions

• Blood Counts: Regular monitoring of white blood cells, red blood cells, and platelets is essential to detect and manage bone marrow suppression.
• Organ Function Tests: Kidney, liver, and cardiac function tests should be done periodically, especially with agents known for specific organ toxicity.
• Infection Prevention: Due to immunosuppression, patients are advised to avoid infections, and prophylactic antibiotics or antifungals may be prescribed.
• Symptom Management: Antiemetics, pain relievers, and nutritional support may be used to manage chemotherapy side effects.

Common Chemotherapy Agents: Uses and Side Effects