USMLE STEP 1 • PHARMACOLOGY

CHEMOTHERAPY
MASTER MAP

Phase → mechanism → toxicity → rescue. Tap through the three views.

Where each class hits

G1growth

SDNA synthesis blockers

G2bleomycin + etoposide

Mmicrotubules

Cell-cycle nonspecific: alkylators, platinum drugs, doxorubicin. They hit DNA regardless of phase.

S = Synthesis. G2 = Bleo + Etop. M = Microtubules. Cross-linkers ignore the schedule.

Cyclophosphamide / ifosfamideDNA cross-linksHemorrhagic cystitis → MESNA; infertility, secondary malignancy

CisplatinDNA cross-linksNephrotoxicity + ototoxicity + neuropathy

MethotrexateDHFR inhibitionMucositis + marrow suppression → leucovorin rescue

5-FU / capecitabineThymidylate synthase inhibitionDiarrhea, mucositis, hand-foot syndrome; DPD deficiency → severe toxicity

DoxorubicinFree radicals + topo IIDilated cardiomyopathy → dexrazoxane

BleomycinFree-radical DNA breaks; G2Pulmonary fibrosis, skin toxicity; little marrow suppression

EtoposideTopo II inhibition; G2Myelosuppression + secondary AML

Irinotecan / topotecanTopo I inhibitionSevere diarrhea; UGT1A1 variation ↑ irinotecan toxicity

VincristineBlocks microtubule polymerization; MPeripheral neuropathy, ileus, SIADH; little marrow toxicity

VinblastineBlocks microtubule polymerization; MMyelosuppression

Paclitaxel / docetaxelStabilize microtubules; MNeuropathy, myelosuppression, hypersensitivity

DOXO = damaged heart

Cardiomyopathy → dexrazoxane

BLEO = bad lungs

Pulmonary fibrosis; little marrow toxicity

CISPLATIN = kidney + ear

Nephrotoxicity, ototoxicity, neuropathy

VINCRISTINE = vicious nerves

Neuropathy, ileus, SIADH

Vincas prevent microtubule polymerization. Taxanes stabilize microtubules.

Leucovorin rescues methotrexate—but enhances 5-FU.

Irinotecan = diarrhea. Etoposide = secondary AML.

Bleomycin = lungs without major marrow suppression.

Tumor lysis syndrome: ↑K⁺, ↑PO₄³⁻, ↓Ca²⁺, ↑uric acid → hydration + allopurinol or rasburicase.

MESNA → bladderLEUCOVORIN → MTXDEXRAZOXANE → heartAMIFOSTINE → kidney