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Editorial |
1 From the Magnetic Resonance Science Center, Department of Radiology, University of California, San Francisco, 1 Irving St, Room AC-109, San Francisco, CA 94143-1290. Received May 16, 2000; accepted May 23. Address correspondence to the author (e-mail: Nola.Hylton@radiology.ucsf.edu).
Index terms: Contrast media, complications, **.121432, **.58 • Contrast media, effects, **.12143, **.58 • Contrast media, toxicity, **.12143, **.58 • Editorials • Gadolinium, **.12143 • Magnetic resonance (MR), contrast media, **.12143
A precautionary 24-hour suspension of breast-feeding is generally recommended following the administration of a gadolinium-containing contrast agent for magnetic resonance (MR) imaging. In the article "Excretion of Gadopentetate Dimeglumine into Human Breast Milk during Lactation," Kubik-Huch and colleagues tested serial samples of expressed breast milk from 20 lactating women over a minimum of 24 hours following the administration of gadopentetate dimeglumine (1).
The gadolinium concentration of the samples was analyzed by using inductively coupled plasma atomic emission spectroscopy. Cumulative amounts of gadolinium were compared with the amounts of gadolinium in standard doses of intravenously administered contrast material prescribed in MR imaging examinations of neonates. On the basis of the finding that the amount of gadopentetate dimeglumine transferred orally was more than 100 times below the permitted intravenous dose for neonatal MR imaging examinations, the authors questioned the justification for the 24-hour suspension of breast-feeding in lactating women and suggested its reconsideration.
The recommendation for 24-hour suspension has been used as a precautionary measure because of the lack of data with regard to the levels of gadolinium excreted in breast milk and the unknown risk to newborns. However, there are increasing data demonstrating the safety of standard intravenous gadolinium-containing contrast agents in infants and children. The safety profiles of gadopentetate dimeglumine and gadodiamide are well established, and the use of these contrast agents in neonates is reported without adverse consequences of clinically important severity (2,3).
In the study by Kubik-Huch and colleagues, among the 18 women receiving a single dose of gadopentetate dimeglumine, the highest cumulative level of excreted gadolinium was measured to be 0.003 mmol, which is more than 100 times lower than the permitted intravenous dose of 0.2 mmol per kilogram of body weight for neonatal imaging. The amount of excreted gadolinium was found to increase with both the volume of contrast agent injected and the volume of milk expressed. However, even in extreme cases of mother’s weight and injected dose, the amount of gadolinium ingested by the breast-feeding infant was projected to be less than 10% of the safe dose levels for neonatal MR imaging examinations.
As noted by the authors, the risk-benefit considerations for a neonatal contrast agent–enhanced MR imaging examination do not apply to a normal breast-feeding newborn. Nonetheless, the authors found very low levels of excreted gadolinium, which is subsequently ingested by the infant. Intestinal absorption of gadolinium is known to be extremely low and presents little risk. What is absorbed is excreted efficiently through the kidneys. Several large studies of the safety associated with oral contrast agents have found gadolinium-containing compounds to be very safe and well tolerated, with fewer adverse effects experienced with orally administered contrast agents than with intravenously administered agents (4,5).
There have been few prior data with regard to the levels of gadolinium excreted in human breast milk. Investigators in two case studies (6,7) referenced by the authors measured the amount of excreted gadolinium in the breast milk over 24 hours to be in the same range as in the group of women in the study by Kubik-Huch et al. The data presented by the authors represent an important contribution to the body of data in this area.
Certainly, additional studies are warranted. While it may be premature to remove the 24-hour recommendation, it may be reasonable to consider reducing the length of the suspension. The amount of gadolinium in the samples was shown to decrease significantly with time. In the data presented, the greatest decrease in excretion levels occurred in the first 12 hours in most cases. A cautious approach to softening the recommendation may be to reduce the suspension to 12 hours initially. It may still be prudent to continue longer suspensions in certain individuals. One individual with mastitis produced only one sample of 2.5 mL and showed a considerably higher gadolinium concentration than the others in the study. This might suggest that there are cases when a recommendation for 24-hour suspension of breast-feeding is still appropriate, such as in women with mastitis or other conditions that cause a reduced milk supply (other than weaning, which was shown here not to result in higher excretion levels).
These data apply to single doses of gadopentetate dimeglumine. While the one patient included in the study who received a double dose (0.2 mmol/kg) had excreted levels of gadolinium that were within the range of the other subjects, it cannot be concluded on this basis that dose has no effect on excreted levels, and intuitively this is not the case.
With the data demonstrating the safety of intravenous and oral gadolinium-containing contrast agents in infants and the low amounts of gadolinium found to be excreted in human breast milk, it is timely to reconsider the justification for a 24-hour precautionary suspension of breast-feeding following gadolinium-containing contrast agent administration. The need for a 24-hour suspension must be weighed against the distress to mother and infant resulting from the disruption in breast-feeding. There is also the risk that the mother might delay her test in order not to interrupt breast-feeding. Rather than issue a blanket recommendation in this regard, it might be preferable to allow the mother to make an informed decision to temporarily stop breast-feeding on the basis of the data regarding excreted levels of gadolinium and the safety of gadolinium in neonates and infants.
In summary, the findings reported by Kubik-Huch et al are important in understanding the actual risks involved in breast-feeding following contrast-enhanced MR imaging and are cause to review the recommendations for 24-hour suspension.
FOOTNOTES
See also the article by Kubik-Huch et al in this issue (pp 555–558 ).
REFERENCES
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