Information in this record refers to the use of strontium 89 as a therapeutic agent. No information is available on the therapeutic use of strontium 89 during breastfeeding. It has been estimated that about 9% of the strontium in the maternal bloodstream reaches breastmilk for another strontium isotope, strontium 90.[1] Because strontium can substitute for calcium in infant bones, the manufacturer and expert opinion recommend discontinuing breastfeeding before a nursing mother receives strontium 89 chloride.[2]