Detection of lithium in breast milk and the mammary glands

Lithium is a key component in many anti-psychosis medications and can be transmitted to the breast-fed infants of medicated mothers. Using laser induced breakdown spectroscopy (LIBS), trace lithium levels are observed in the breast milk of lactating rats administered with lithium postpartum with limit of detection of LIBS about 0.1 ppm. Subsequently, the mammary glands of female rats were analyzed using LIBS and inductively coupled plasma mass spectrometry. Lithium at 1.06 μg/g concentration was measured in the mammary glands of lithium medicated subjects, but was below the limit of detection in controls. Lithium also increases iodine content (p<0.05), decreases phosphorus content, and increases the calcium/phosphorus ratio in the glands (p<0.05). Lithium is present in the breast milk and mammary glands of medicated female subjects and this is the likely route of entry to breast-fed infants. Lithium use in pre-partum has been associated with a number of negative effects in the newborn. These effects are conventionally resolved by reducing the pre-partum dose. However, current practice guidelines in post-partum discourage use of lithium during breast-feeding due to transient abnormalities of thyroid-stimulating hormone and blood urea nitrogen. This however, denies the infant the many benefits of breast feeding, or requires the mother to stop or change medications. The most recent guideline is still cautious as there is little evidence beyond a handful of case reports. Therefore, there is significant need for further research. This study helps establish the rat as an animal model for studying the biodistribution of lithium.