Nitroprusside and Breastfeeding

Summary of use during lactation

Breastmilk levels of nitroprusside sodium have not been measured after exogenous administration. Because of its short half-life of 2 minutes, it is unlikely to appear in breastmilk. However, its toxic metabolite, thiocyanate, is excreted into milk and can be directly toxic to the infant as well as inhibiting iodide transport into breastmilk. Cyanide is another toxic metabolite of nitroprusside that may enter breastmilk. An alternate drug is therefore preferred during breastfeeding. If use of nitroprusside sodium is unavoidable, the mother should refrain from breastfeeding.

Drug levels in milk and infant serum

Nitroprusside is converted with a half-life of about 2 minutes to cyanide and then to thiocyanate in the body. Both of these metabolites have longer half-lives: 7.3 hours for cyanide and an estimated 3 days to 2 weeks for thiocyanate.[1] Maternal Levels. An older study found that thiocyanate passed into human breastmilk in concentrations from 27% to 50% of maternal serum levels.[2] A later study found milk levels to range from 16% to 42% of maternal plasma levels.[3] A 2004 study found values ranging from 42% to 82%,[1] while a more recent study reported fractional excretion of thiocyanate that ranged between 1.4-14.4%.[4] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

Several studies have found that breastmilk iodine levels are inversely related to the mothers' blood thiocyanate levels, probably through inhibition of the Na/I symporter by thiocyanate.[5-8] However, a recent study failed to demonstrate such a correlation. The authors felt that the effect of thiocyanate on iodine transport may be less pronounced than previously reported.[4] These low breastmilk iodine levels might pose a risk of hypothyroidism to breastfed infants whose mothers have low iodine intake.[4-8]

Effects on lactation and breastmilk

Relevant published information was not found as of the revision date.

Alternative drugs to consider

Candesartan, Benazepril, Captopril, Enalapril, Lisinopril, Quinapril, Hydralazine, Hydrochlorothiazide, Methyldopa, Propranolol

References

1. Dorea JG. Maternal thiocyanate and thyroid status during breast-feeding. J Am Coll Nutr 2004;23:97-101.15047674 PubMed
2. Funderburk CF, Van Middlesworth L. Effect of lactation and perchlorate on thiocyanate metabolism. Am J Physiol 1967;213:1371-7.4294711 PubMed
3. Meberg A, Sande H, Foss OP, et al. Smoking during pregnancy--effects on the fetus and on thiocyanate levels in mother and baby. Acta Paediatr Scand 1979;68:547-52.463536
4. Dasgupta PK, Kirk AB, Dyke JV, et al. Intake of iodine and perchlorate and excretion in human milk. Environ Sci Technol 2008;42:8115-21.19031911 PubMed
5. Vanderpas J, Rivera MT, Berquist H, et al. Thiocyanate overload decreases iodine supply in iodine-deficient breast-fed infants. Horm Res 2007;68 (Suppl. 3):53-4.17228181 PubMed
6. Leung AM, Braverman LE, He X, et al. Environmental perchlorate and thiocyanate exposures and infant serum thyroid function. Thyroid 2012;22:938-43.22827469 PubMed
7. Laurberg P, Nohr SB, Pedersen KM, et al. Iodine nutrition in breast-fed infants is impaired by maternal smoking. J Clin Endocrinol Metab 2004;89:181-7.14715847 PubMed
8. Kirk AB, Dyke JV, Martin CF, et al. Temporal patterns in perchlorate, thiocyanate, and iodide excretion in human milk. Environ Health Perspect 2007;115:182-6.17384762 PubMed