Drug Levels and Effects:

Summary of Use during Lactation:

Most sources consider breastfeeding to be contraindicated during maternal antineoplastic drug therapy.

Drug Levels:

Maternal Levels.

Unmetabolized cyclophosphamide has been qualitatively detected in milk 1, 3, 5 and 6 hours after an intravenous injection of 500 mg of drug in one patient.[1][2] Quantitative determination has not been reported.

Infant Levels.

Relevant published information was not found as of the revision date.

Effects in Breastfed Infants:

In one 23-day-old infant, neutropenia, thrombocytopenia and a low hemoglobin were possibly caused by cyclophosphamide after 3 days of maternal treatment with cyclophosphamide 6 mg/kg intravenously daily (total dose 300 mg).[3]

In a 4-month-old, neutropenia was probably caused by cyclophosphamide in a mother 9 days after the last of 6 weekly doses of 800 mg cyclophosphamide intravenously, 2 mgvincristineintravenously and daily doses of 30 mg of prednisolone orally. Neutropenia persisted at least 12 days and was accompanied by a brief episode of diarrhea.[4]

Possible Effects on Lactation:

Relevant published information was not found as of the revision date.

Alternate Drugs to Consider:

Dependent on the condition being treated.


1. Duncan JH, Colvin OM, Fenselau C. Mass spectrometric study of the distribution of cyclophosphamide in humans. Toxicol Appl Pharmacol. 1973;24:317-23. PMID:4741053
2. Wiernik PH, Duncan JH. Cyclophosphamide in human milk. Lancet. 1971;1(7705):912. PMID:4102054
3. Durodola JI. Administration of cyclophosphamide during late pregnancy and early lactation: a case report. J Nat Med Assoc. 1979;71:165-6. PMID:423292
4. Amato D, Niblett JS. Neutropenia from cyclophosphamide in breast milk. Med J Aust. 1977;1:383-4. PMID:859486

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Antineoplastic Agents

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

    Disclaimer:Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.