The use of iodinated or gadolinium-based contrast media in pregnant or lactating women often causes concerns in the radiology department because of the principle of not exposing a fetus or neonate to any drugs. Because of the uncertainty about the use of contrast media during pregnancy and lactation, the Contrast Media Safety Committee of the European Society of Urogenital Radiology decided to review the literature and draw up guidelines. An extensive literature search was carried out and summarized in a report. Based on the limited information available, simple guidelines have been drawn up. The report and guidelines were discussed at the 11th European Symposium on Urogenital Radiology in Santiago de Compostela, Spain. Mutagenic and teratogenic effects have not been described after administration of gadolinium or iodinated contrast media. Free iodide in radiographic contrast medium given to the mother has the potential to depress fetal/neonatal thyroid function. Neonatal thyroid function should be checked during the 1st week if iodinated contrast media have been given during pregnancy. No effect on the fetus has been seen after gadolinium contrast media. Only tiny amounts of iodinated or gadolinium-based contrast medium given to a lactating mother reach the milk, and only a minute proportion entering the baby's gut is absorbed. The very small potential risk associated with absorption of contrast medium may be considered insufficient to warrant stopping breast-feeding for 24 h following either iodinated or gadolinium contrast agents.

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The use of iodinated and gadolinium contrast media during pregnancy and lactation.

It has been known since the last century that maternal milk sometimes may contain chemical contaminants which could have adverse effects on nursing infants. Such experiences came mainly from cases of exposure to occupational chemicals or drugs. Since 1950, it has further been known that human milk may contain potentially hazardous persistent environmental chemicals in concentrations higher than in cow’s milk.

Chemical Contaminants in Human Milk

Breast-feeding is the best method of feeding neonates and young infants.1 Its popularity has increased in recent years,2 although in 1995 only about 60 percent of new mothers in the United States were breast-feeding their infants at the time of hospital discharge.3 Current recommendations suggest that in the absence of contraindications, women should breast-feed their infants for at least the first 12 months of life. However, many mothers are likely to need to take medications at some point during this time.4,5 The possible effects of these medications on breast-fed infants are therefore of great concern. Benefits of Breast-Feeding Breast-feeding . . .

Drug Therapy for Breast-Feeding Women

Blood and/or breast milk have been used to assess human exposure to various environmental contaminants. Few studies have been available to compare the concentrations in one matrix with those in another. The goals of this study were to determine the current levels of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in Japanese women, with analysis of the effects of lifestyle and dietary habits on these levels, and to develop a quantitative structure-activity relationship (QSAR) with which to predict the ratio of serum concentration to breast milk concentration. We measured PBDEs and PCBs in 89 paired samples of serum and breast milk collected in four regions of Japan in 2005. The geometric means of the total concentrations of PBDE (13 congeners) in milk and serum were 1.56 and 2.89 ng/g lipid, respectively, whereas those of total PCBs (15 congeners) were 63.9 and 37.5 ng/g lipid, respectively. The major determinant of total PBDE concentration in serum and milk was the geographic area within Japan, whereas nursing duration was the major determinant of PCB concentration. BDE-209 was the most predominant PBDE congener in serum but not in milk. The excretion of BDE 209 in milk was lower than that of BDE 47 and BDE 153. QSAR analysis revealed that two parameters, calculated octanol/water partition and number of hydrogen-bond acceptors, were significant descriptors. During the first weeks of lactation, the predicted partitioning of PBDE and PCB congeners from serum to milk agreed with the observed values. However, the prediction became weaker after 10 weeks of nursing.

Levels and concentration ratios of polychlorinated biphenyls and polybrominated diphenyl ethers in serum and breast milk in Japanese mothers.

Rational pharmacotherapy is dependent upon an understanding of the clinical pharmacokinetic and pharmacodynamic properties of the drugs employed. Although the available data on drug biodisposition and action in the neonate have increased considerably in the last few years, pharmacokinetic-pharmacodynamic interactions for many drugs remain poorly understood.

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Principles of Drug Biodisposition in the Neonate

The excretion of drugs in human breast milk is reviewed with regard to milk production, composition, feeding patterns and mechanisms of drug transfer into milk. Fundamental principles of breast milk excretion are used to construct a pharmacokinetic approach useful for the study of most drugs. An infant-modulated 3-compartment open model is proposed for drug distribution and elimination in the breast feeding woman. Milk/plasma drug concentration ratios are projected on the basis of pH partitioning. While some studies confirm these projections, other studies demonstrate a need to consider additional factors such as lipid solubility and protein binding characteristics of a drug in milk.

Drug excretion in human breast milk: principles, pharmacokinetics and projected consequences.

We hold these truths to be self-evident. The concentration of a drug in milk is time dependent. Concurrence does not necessarily exist between milk and plasma drug concentra­ tion profiles. Presumed concurrence undermines the study design and weakens the reliability of data. A pharmacokinetic model is a requisite foundation for studies of drugs in breast milk. A test of the �del applicable to each drug allows the most accurate estimates of the milk-to-plasma (M/P) ratio. Pragmatic utilization of study data is often a function of a valid M/P ratio as it impacts on an assessment of dose and safety for the nursing infant.

R D Brown

Papers

Drug excretion in human breast milk: principles, pharmacokinetics and projected consequences.

Pharmacokinetic pitfalls in the estimation of the breast milk/plasma ratio for drugs.