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Topoisomerase I inhibitor

Irinotecan

Camptosar

How it works

Inhibits topoisomerase I, preventing DNA religation. Used in mFFX.

Irinotecan's cholinergic and diarrheal toxicity requires close GI monitoring. Patients must have rescue loperamide on hand. UGT1A1*28 homozygotes need dose reduction from the outset.

Dosing

Typical doses

  • 150 mg/m² IV

Schedule

  • Day 1 of 14-day mFFX cycle
    cycle_linked

Side Effects

  • •Acute cholinergic syndrome (0–24h post-dose): salivation, lacrimation, sweating, cramping, diarrhea
  • •Delayed diarrhea (D3–7) — can be severe, requiring loperamide
  • •Nausea, vomiting
  • •Fatigue, weakness
  • •Alopecia
  • Severe delayed diarrhea Grade 3+ (≥7 stools/day) — dehydration risk
  • Neutropenic enterocolitis (febrile neutropenia + diarrhea) — medical emergency

Monitoring

  • Atropine IM at first sign of acute cholinergic symptoms (within 24h of dose)
  • Loperamide at onset of loose stool; escalate if ≥4 stools/day
  • FBC, U&Es, LFTs

Diet & Food Interactions

Alcohol
Increases risk of diarrhea and GI upset