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

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.