Skip to Content

Iobenguane I 131 use while Breastfeeding

Iobenguane I 131 Levels and Effects while Breastfeeding

Summary of Use during Lactation

Information in this record refers to the use of iobenguane I 131 (I 131 meta-iodobenzylguanidine; I 131 MIBG) as a diagnostic agent. The International Commission on Radiological Protection states that breastfeeding should be interrupted for more than 3 weeks following diagnostic use of I 131 MIBG. This usually will result in permanent discontinuation of breastfeeding for this infant, and cessation of breastfeeding for the current infant is recommended by most experts.[1][2] Patients receiving iobenguane I 131usually receive potassium iodide prior to the diagnostic examination to block their thyroid gland's uptake of the I-131 that is released from the I 131 MIBG. Iodide may interfere with the infant's thyroid function.

Nursing mothers should not work with substances containing I 131 in their workplace.[3]

Drug Levels

I 131 is a beta and high-energy gamma emitter with a main gamma emission energy of 364 keV and a physical half-life of 8.04 days.[4] Iodide is actively secreted into breastmilk and actively taken up by the mother's and infant's thyroid glands.

Effects in Breastfed Infants

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

Effects on Lactation and Breastmilk

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


1. Bombardieri E, Giammarile F, Aktolun C L et al. 131I/123I-metaiodobenzylguanidine (mIBG) scintigraphy: procedure guidelines for tumour imaging. Eur J Nucl Med Mol Imaging. 2010;37:2436-46. PMID: 20644928

2. Mattsson S, Johansson L, Leide Svegborn S et al. Radiation dose to patients from radiopharmaceuticals: A compendium of current information related to frequently used substances. Annex D. Recommendations on breast-feeding interruptions. Ann ICRP. 2015;44 (2 Suppl):319-21. PMID: 26069086

3. Howe DB, Beardsley M, Bakhsh S. Appendix U. Model procedure for release of patients or human research subjects administered radioactive materials. In, NUREG-1556. Consolidated guidance about materials licenses. Program-specific guidance about medical use licenses. Final report. U.S. Nuclear Regulatory Commission Office of Nuclear Material Safety and Safeguards. 2008;9, Rev. 2.

4. Almen A, Mattsson S. Radiological protection of foetuses and breast-fed children of occupationally exposed women in nuclear medicine - Challenges for hospitals. Phys Med. 2017;43:172-7. PMID: 28882410

Iobenguane I 131 Identification

Substance Name

Iobenguane I 131

CAS Registry Number


Drug Class


Iodine Radioisotopes

Administrative Information

LactMed Record Number


Last Revision Date



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.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.