Iodine-123
Radioactive iodine is concentrated in thyroid and breast milk and may suppress thyroid function in infants.
The I-123 is used as a diagnostic agent. Its mean physical radioactive lifetime is 13.2 hours (Howe 2008) and the half-life of biodegradation is 4.8 to 10.2 hours (Stabin 2000). After 10 physical half-lives, the element ceases to have significant radioactivity and after 5 biological half-lives its concentration in the milk is negligible.
If you want to limit exposure to 0 mili Servers (mSv), you should stop breast-feeding for a period equivalent to from 5 to 10 biological half-lives. It is also possible to determine the radioactivity in milk samples.
Since the annual natural background radiation we receive is around 6 mSv, for a more conservative approach we should wait just long enough to achieve an infant exposure of less than 1 mSv (0.1 rem)
The iodine-123 that is administered to nursing mothers must be pure, that means, without containing traces of I-124 and I-125
Recommended time for transient weaning to ensure reducing exposure to 1 mSv:
I-123 as sodium iodine hippurate or orto-iodo hippurate (123 I-OIH): Doses up to 100 MBq (4 mCi) waiting time= 8 to 12 hours. According to Nuclear Regulatory Commission of the United States: it is not necessary to stop breastfeeding.
I-123 as sodium iodide (123 I-NaI). If uncontaminated with I 125: doses up to 20 MBq (0.5 mCi) waiting time= 3 to 6 hours. If contaminated: ICRP (Mattsson 2015, Sachs 2013, ICRP 2008): > 3 weeks, The American Thyroid Association (Alexander 2017 Q91 R77): 3 to 4 days
I-123 as iobenguane (I-123 meta-iodobenzylguanidine, I-123-MIBG). If uncontaminated I 123, discontinue breastfeeding for 12, 24 or 48 hours depending on whether the dose was 150, 370 or 400 MBq (4, 10 or 11 mCi). With contamination of I 124 or I 125, the interruption period is >3 weeks (Sachs 2013, ICRP 2008).
I-123 as ioflupane: Stop breastfeeding from 1 day (Society of Nuclear Medicine, Djang 2012) to 6 days (the manufactured).
I 123-Labeled Human Serum Albumin (123 I-HSA): > 3 weeks (Sachs 2013, ICRP 2008).
I 123-Iodofiltic Acid (beta-methyl-15-(4-iodophenyl) pentadecanoic acid; I 123 BMIPP): > 3 weeks (Sachs 2013, ICRP 2008).
I 123-phenylpentadecanoic acid (123 I-IPPA): > 3 weeks (Sachs 2013, ICRP 2008).
For more safety, you can request to measure the amount of radioactivity of the milk in the nuclear medicine service.
If you want to continue breastfeeding, extraction and storage of breast milk in a freezer for days or weeks must be previously ensured. During the suggested days for interruption of breastfeeding after the test is done, the child can be fed exclusively with the milk previously stored or using both breast milk and formula.
After the test you can continue extracting and storing the milk in a separated freezer for 10 physical half-lives (132 hours = 5.5 days, once radiation is gone and it can be used for feeding the baby).
Mothers receiving a dose as lower as 400 MBq for a thyroid scan are not in need to refrain from close contact with their children.
Alternatives
- Technetium 99m sestamibi (Low Risk probable)
Very Low Risk
Compatible. Not risky for breastfeeding or infant.
Low Risk
Moderately safe. Mild risk possible. Follow up recommended. Read the Comment.
High Risk
Poorly safe. Evaluate carefully. Use a safer alternative. Read the Comment.
Very High Risk
Not recommended. Cessation of breastfeeding or alternative.
Synonyms
- i 123 Iobenguane (I-123 meta-iodobenzylguanidine; I-123-MIBG)
- I-123 Iodofiltic Acid (beta-methyl-15-(4-iodophenyl) pentadecanoic acid; 123 I-BMIPP)
- I-123 Iodohippurate Sodium (I-123 orto-iodo hippurate; 123 I-OIH)
- I 123 Ioflupane
References
- Alexander EK, Pearce EN, Brent GA, Brown RS, Chen H, Dosiou C, Grobman WA, Laurberg P, Lazarus JH, Mandel SJ, Peeters RP, Sullivan S. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid. 2017Abstract Full text (link to original source) Full text (in our servers)
- ARSAC: Administration of Radioactive Substances Advisory Committee. Notes for Guidance on the Clinical Administration of Radiopharmaceuticals and Use of Sealed Radioactive Sources. Section 7 Conception, Pregnancy and Breastfeeding, p. 25-30. ARSAC Support Unit. Centre for Radiation, Chemical and Environmental Hazards. Public Health England. 2016Abstract Full text (link to original source) Full text (in our servers)
- Leide-Svegborn S, Ahlgren L, Johansson L, Mattsson S. Excretion of radionuclides in human breast milk after nuclear medicine examinations. Biokinetic and dosimetric data and recommendations on breastfeeding interruption. Eur J Nucl Med Mol Imaging. 2016Abstract
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- ICRP. Radiation dose to patients from radiopharmaceuticals. Addendum 3 to ICRP Publication 53. ICRP Publication 106. Annex D. Recommendations on breast-feeding interruptions, p. 163-165. Ann ICRP. 2008Abstract Full text (link to original source) Full text (in our servers)
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