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Pharmacology · Chapter 3

The Cell Cycle & Where Chemo Strikes

Antineoplastics don't kill cancer cells — they kill dividing cells. Where a drug lands on the cell cycle predicts what it destroys, which healthy tissue it wrecks, and what you monitor. Tap a phase on the wheel, or tap a drug class to see where it lands.

The cell cycle

G0 resting G1 S G2 M
Five phases, five targetstap the wheel or a drug class
Growth fraction is everythingChemotherapy hits cells that are actively cycling. A tumor with a high growth fraction (leukemias, lymphomas, testicular cancer) melts away; a slow, bulky solid tumor sitting mostly in G0 barely flinches. The same rule explains the toxicity profile: your bone marrow, GI mucosa, and hair follicles divide fastest, so they get hurt first — myelosuppression, mucositis, and alopecia.
Nurse: the two questions that drive every chemo shift are what's the ANC? and when is the nadir?