Which of the following is a cell cycle-specific drug that targets the M phase?

RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Pharmacology

Easy

Appeared in: RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Explanation

Paclitaxel is classified as a mitotic spindle inhibitor, specifically a taxane.
Its mechanism of action involves inhibiting the depolymerization of tubulin, which stabilizes microtubules.
This stabilization arrests the cell in the M phase (mitosis) of the cell cycle, as the mitotic spindle cannot function correctly to separate chromosomes.
Because it acts on a specific phase, it is known as a cell cycle-specific (CCS) agent.

Option A: Methotrexate is a cell cycle-specific drug, but it targets the S phase (DNA synthesis), not the M phase.
Option B: Cisplatin is a cell cycle-nonspecific (CCNS) agent. It acts by cross-linking DNA, which can damage the cell at any point in the cell cycle, including the resting (G0) phase.
Option C: Cyclophosphamide is an alkylating agent and is cell cycle-nonspecific (CCNS). Like cisplatin, it damages DNA regardless of the cell's phase.

Visual 1: Diagram - A diagram of the cell cycle (G0, G1, S, G2, M phases) with arrows indicating the point of action for different classes of chemotherapy drugs (e.g., Antimetabolites at S phase, Mitotic inhibitors at M phase, Alkylating agents acting on all phases). This visual helps to map the drugs to their specific targets in the cellular process.
Visual 2: Flowchart - A flowchart illustrating the mechanism of Paclitaxel: Paclitaxel administration -> Binds to tubulin -> Microtubule stabilization -> Prevents depolymerization -> Mitotic spindle cannot form/break down -> Cell arrested in M phase -> Apoptosis (cell death).

Clinical Relevance

Nursing practice connection: Knowing Cell cycle specificity of chemotherapeutic agents helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses administering Paclitaxel must monitor for side effects related to M-phase arrest, particularly peripheral neuropathy and myelosuppression, as nerve cells and bone marrow cells are affected.
A key nursing intervention for Paclitaxel is premedication with corticosteroids, H1 and H2 antagonists to prevent severe hypersensitivity reactions, which are common with this drug.
Understanding cell cycle specificity helps in patient education. A nurse can explain that side effects like hair loss and mouth sores occur because the chemotherapy targets all rapidly dividing cells, not just cancer cells.

How to Approach the Question

First, identify the key terms in the question: 'cell cycle-specific' and 'M phase'. This tells you the question is asking for a drug that only works during the mitosis stage of cell division.
Next, recall the major classes of chemotherapy drugs and their cell cycle specificity. Group them mentally: Antimetabolites (S phase), Mitotic Inhibitors (M phase), Alkylating Agents (nonspecific), etc.
Evaluate each option against this classification:
Methotrexate: Recall it's an antimetabolite, which acts on the S phase. Eliminate.
Cisplatin: Recall it's an alkylating-like agent, which is cell cycle-nonspecific. Eliminate.
Cyclophosphamide: Recall it's an alkylating agent, also cell cycle-nonspecific. Eliminate.

Concept Tested & Keywords

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