Breast milk is best. That much is known. It’s the ideal source of nutrition for babies, full of white blood cells that boost a newborn’s immune system, and a timeless contributor to the mother-infant bond.

But what if mom is taking prescription or other drugs? At what point do the risks associated with these chemicals, which can be passed to the baby through mother’s milk, outweigh the value of nursing?

Can a mom afford to have a drink, for instance? The answer is yes, but if she’s going to have more than one, she should wait until the alcohol clears her system before breastfeeding. Feeding the baby after taking more than one standard drink could be unsafe. Heavy drinking by the mother can cause drowsiness, weakness, decreased growth and abnormal weight gain in a breastfed infant.

Despite the breast’s natural filtration system, traces of most drugs end up in milk. But according to the American Academy of Pediatrics (AAP), relatively few are thought to be harmful to the breast-fed infant, even at excessive doses.

Dr. Ruth Lawrence, a pediatrician and breastfeeding expert at the University of Rochester in New York, says the key thing to remember is that mothers, unlike cows, produce most of their milk while the baby is feeding - very little is stored. That means, as long as the mother has cleared a drug from her system, it won’t be present in the milk at significant levels. "It’s what is in the mother’s blood at the time of feeding that gets in the milk," says Lawrence.

In 1994, the AAP scoured the medical literature and made recommendations on which drugs nursing mothers should be concerned about and which are probably safe. The association’s warning list includes some antibiotics, certain antihistamines, nicotine, excessive alcohol, lithium (used to treat mental illnesses such as bipolar disorder) and all recreational drugs.

Lawrence, who led the AAP breastfeeding task force on the 1994 study, cautions that these drug tables may appear more dire than is really the case. For instance, so long as a mom who smokes waits a couple of hours between her last cigarette and a breastfeeding, the infant won’t ingest significant nicotine. Smoking in a baby’s presence is far worse for the child, she says.

Even some of the more problematic drugs such as those used for chemotherapy may not be a reason for a mother to stop breastfeeding entirely, says Lawrence. But it is important is that the mother not feed the child just after taking a drug. "We know the half-lives of these drugs," she says. "We know when it clears, and we suggest that the mother pump and discard the milk during treatment, and breastfeed in between treatments."

Antidepressants, whose long-term effects on infants are largely unknown, are widely prescribed to mothers. And not surprisingly so: According to the American Counseling Association, 80 percent of women experience what is sometimes called the “baby blues,” and up to 20 percent experience postpartum depression. In the short term, at least, most of the common antidepressants are considered safe for breast-fed infants, says Lawrence.

To determine safety, researchers typically look at the level of a drug in the baby’s blood and document observations by pediatricians and parents concerning behavior of the infants. Since these drugs work on the brain, however, adverse reactions may be hard to detect, so how much of the drug ends up in the baby’s system is weighed more heavily. According to the AAP, however, most of the drugs that are considered harmful are deemed as such based on the anecdotal evidence.

For instance, the American Journal of Psychiatry published a study in February looking at paroxetine, part of a widely used class of antidepressants known as selective serotonin reuptake inhibitors, or SSRIs. Although the 16 breast-fed infants of mothers taking the drug had low, detectable levels of the drug in their blood, no short-term ill effects were reported by parents or pediatricians, a result the authors say is in line with other SSRI studies.

But such results may not be sufficient to ease a mother’s fears. Penelope Bremer, a 29-year-old San Francisco-area mom, suffered two bouts of postnatal depression, the first three years ago. Her doctor would not prescribe Prozac at the time, she says, because too little was known about the drug. Bremer’s depression went untreated until finally, concerned for her safety, she checked herself into a hospital psychiatric ward.

At that point, her doctor prescribed the drug.

Four months ago, Bremer again sought antidepressants for postpartum depression. Citing new studies, her doctor told her that Prozac is now considered to be safe for nursing mothers. "There were no immediate effects on my children," says Bremer. "But I live in dread that one day they’ll reveal some awful thing that is happening to Prozac babies."

Unnecessary drugs should be avoided while pregnant or breastfeeding, says Lawrence. However, she says, the risks associated with untreated maternal depression and the benefits of breast milk far outweigh any potential danger to the infant from residual antidepressants.

Nevertheless, Lawrence urges mothers to discuss any drugs they are taking, including over-the-counter remedies, with their doctor. "Just because you don’t need a prescription doesn’t mean the drug is safe," she says. "Some herbal drugs, the best known being St. John’s Wort, contain an SSRI. If you take that along with your prescription antidepressant, you are increasing the dose."

Common headache remedies and painkillers should be used sparingly, Lawrence adds, and after consultation with a physician. If a mother must use any drug whose safety is in doubt, she should watch the infant’s reactions carefully, and doctors may consider monitoring the concentration of the drug in the nursing infant’s blood. Drug exposure to the baby can be minimized if the medication is taken just after breastfeeding, or just before the infant is due to sleep for a long period of time. This, of course, presumes that the infant ever sleeps for a long period of time.

© 2007 Green Home, Inc.