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Release: Nov. 14, 2000

UI researcher investigates anti-depressants and nursing mothers

IOWA CITY, Iowa -- University of Iowa Health Care researchers are looking into the effects of antidepressants on the infants of nursing mothers with postpartum depression.

Numerous studies have been conducted to gauge the extent of exposure of antidepressants in infants of nursing mothers. These studies are intended to provide descriptive data to aid physicians when making the choice of whether or not to prescribe an antidepressant to a breastfeeding mother. The studies have shown that some antidepressants showed higher levels of accumulation in infants' blood. It should be noted that these studies were conducted with a small number of infants, often three or fewer.

A current study headed by Alicia Weissman, M.D., in the University of Iowa Department of Family Medicine involves mothers with postpartum or other depression who have taken one or more antidepressants for at least one week. Weissman and her colleagues measure the amounts of various antidepressants in blood samples from both the mother and infant, and in samples of the mothers' breast milk. These measurements are made in an attempt to discover which antidepressants tend to accumulate in the infant's bloodstream and which ones do not.

Because antidepressants must get into the brain, they pass through the blood-brain barrier, a protective membrane that protects the brain from being exposed to everything that passes through the bloodstream. The same characteristics that allow a drug to pass through the blood-brain barrier also allow the drug to pass into breast milk. Weissman says that all antidepressants will enter breast milk.

"The issue is not whether or not the drug gets in, it's how much and whether it builds up in the baby," she said.

Weissman added that the drug levels in breast milk are not necessarily predictive of the drug levels in an infant. Factors such as the infant's metabolism and the half-life of the drug, or how long it remains in the infant's system, will also affect the levels.

However, Weissman says antidepressants and other substances may accumulate in newborns, who do not have the liver capacity of adults. This is because the liver is responsible for filtering substances that enter the bloodstream.

By looking at the levels of antidepressants in nursing mothers, their breast milk and their newborns, Weissman and her colleagues hope to determine which antidepressant medications may be better suited for nursing mothers.

University of Iowa Health Care describes the partnership between the UI College of Medicine and the UI Hospitals and Clinics and the patient care, medical education and research programs and services they provide.