Passage of irinotecan and its active metabolite, SN‐38, into human milk

Summary What is known and objective We measured the levels of irinotecan and its active metabolite, SN‐38, in human milk after the administration of irinotecan to assess the potential risks when women treated with irinotecan nurse their infants. Case summary Human milk was collected for 6 days starting on the day after irinotecan was administered. The levels of irinotecan and SN‐38 in human milk were measured using liquid chromatography–mass spectrometry. Irinotecan was detected on Days 2 and 3 but not after Day 4. A strong signal indicating the presence of SN‐38 was detected on Day 2 and the signal was readily detected until Day 7, indicating that SN‐38 remained in human milk. What is new and conclusion Intravenously administered CPT‐11 continues to pass into human milk over a prolonged period in the form of its active metabolite, SN‐38. The relationship between administration of CPT‐11 and SN‐38 exposure and toxicity is still not well defined, so patients should avoid nursing their infants while they are being treated with CPT‐11. A strong signal indicating the presence of SN‐38 was detected on Day 2 and the signal was readily detected until Day 7, indicating that SN‐38 remained in human milk.