It is not known if technetium Tc 99m is present in breast milk. According to the manufacturer, the decision to discontinue breastfeeding during therapy should take into account the benefits of breastfeeding to the infant and the diagnostic needs of the mother. Most sources recommended stopping breast-feeding for ≥4 hours (Ahlgren 1985; ICRP 2000; Mountford 1989; Stabin 2000); however, because excretion of technetium Tc 99 pentetate into breast milk can be widely variable, other sources recommended stopping breastfeeding for ≤12 hours (Harding 1995) or longer while monitoring milk concentrations (Rubow 1994).
In general, following the administration of radiopharmaceuticals, women with a well-established milk supply should pump at normal feeding times and discard the milk until breast-feeding may be resumed (Harding 1995; Mountford 1989). Excretion of Technetium Tc 99m into colostrum is widely variable and information is limited; therefore, recommendations related to early breast-feeding cannot be made (Mountford 1989; Rubow 1994). Elective diagnostic procedures should be delayed until breast-feeding has stopped (Parker 2004). Depending on the dose, compliance with regulatory requirements for instructions to the patient and recordkeeping may also be applicable (USNRC 1997).