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June 25, 1960


Author Affiliations

Berkeley, Calif.

From the Alta Bates Hospital Isotope Department.

JAMA. 1960;173(8):872-875. doi:10.1001/jama.1960.03020260012003

The possibility that I131 administered to a lactating woman might appear in the milk and might reach the nurseling in harmful amounts was studied in six nursing mothers. Most of them were already in the process of weaning their babies. The I131 was given by mouth to the mother in doses of either 10 or 30 μc just after the final breast feeding. The quantity of I131 that appeared in the milk secreted in 48 hours after administration was 1.4, 3.9, 0.14, 0.03, 6.2, and 26.8% of the total that had been administered, respectively, to the six mothers. Most of the I131 was secreted during the first 24 hours. It is recommended that candidates for diagnostic tests with I131 be questioned about lactation and that nursing should be interrupted for 24 hours, or, in the case of a large diagnostic or therapeutic dose, until measurements indicate that the I131 content of the milk is no longer significant.