Drugs and breastmilk - includes a checklist for the lactating mom

Drugs and Breastmilk

A nursing woman becomes justifiably concerned about the prospect of taking medication. She is aware that both prescribed and over-the-counter drugs may enter her mile supply and pose a risk to her baby. Convinced of the importance of continued breastfeeding, she asks several questions: Will this drug compromise the quality of my milk? What are the short- and long-term effects on my baby? What other options do I have?

Sometimes, the answers are not known. Other times, chemists, pharmacists, obstetricians, pediatricians, and biomedical specialists are able to provide bits of pertinent information. Ultimately, it is up to the nursing mother to gather together the pieces of the puzzle, evaluate them in light of the current pharmacological picture, and make the best decision for herself and her baby.

How Drugs Enter Breastmilk

The first consideration is whether or not a particular drug will even enter the breastmilk and transfer to the baby's system. Most often, it will. For many drugs, however, the answer is simply not known because scientists do not fully understand how drugs are metabolized and passed into breastmild. Dr. Ruth Lawrence, author of Breastfeeding: A Guide for the Medical Professional, offers this general guideline: "Most ingested drugs appear in milk; drug levels in milk usually do not exceed 1% of ingested dosage and are independent of milk volume." (1) Remember, too, that a drug's action may change when the drug is taken in conjunction with other drugs or with specific foods, and that the same dosage may have different effects on people of different weights and metabolic rates.

Many variables affect the passage of drugs into breastmilk. For one, their level of concentration depends on how they enter the mother's body. Drugs administered intravenously enter the bloodstream directly and appear highly concentrated, whereas those administered orally or intramuscularly take longer to reach the bloodstream and, in the process, become more dilute. Drugs that are less highly concentrated in the bloodstream are usually less highly concentrated in the breastmilk. (2)

For another, some drugs bind to proteins in the mother's blood system, whereas others do not. Among those that do, some portion of the drug attaches to protein cells, while another portion remains freely circulating. Only these free-circulating molecules can pass through into breastmilk. The protein-binding capacity of a drug thus limits to some degree the concentration that baby receives. (3)

Various other characteristics of a drug determine just how much of it might be passed along to baby. For example, highly alkaline drugs (those with high pH values) pass into the milk at higher levels than do more acidic drugs (those with lower pH values). And drugs composed of large molecules, such as insulin and heparin, are unable to enter the milk supply at all. (4)

Dosage, frequency, and timing often come into play. Higher doses of a drug and higher frequencies of administration may transfer greater concentrations into the milk supply. It is important to realize that each drug has a certain peak-effect level, al point at which its action--and its passage into the breastmilk--is a maximized. Beyond this point, the drug's effectiveness subsides, as does its level of concentration inthe milk. To evaluate the peak effect for any particular drug, one must discover how long it takes to reach its peak point andhow long lasting its peak period is. With this information, a nursing mother can reduce her baby's exposure to the drug by coordinating feeding times with nonpeak periods of drug activity.

It is also important to know that the colostrum produced during the first week postpartum is highly permeable. Some drugs that cannot pass through more mature milk can pass through this early milk. (5)

The Effects of Drugs on Infants

If a drug does enter the breastmilk, and if it is passed on to the baby, what effect might it have? It is tempting to assume that the higher the drug level is in the breastmilk, the greater its effect will be on the baby. More important, however, is how well the infant's liver can break down the substance and how well the kidneys can pass it out in the urine. A small amount of a drug that is not assimilated can pose more problems than a large amount that is quickly excreted.

In the first few days of life, a baby's liver is not prepared to metabolize drugs that require a great deal of processing. The newborn's liver is small and has only a limited number of protein sites to which drug molecules can be bonded and passed from the body. Any molecules not broken down in this way may accumulate and cause toxity. Another complication might arise: in the process of utilizing most of its protein sites for drug metabolism, the newborn's liver may not be able to break down the bilirubin that also needs to be processed. The resulting amounts of bilirubin can be unusually high and may cause jaundice. Drugs such as acetaminophen (Tylenol, Datril, and Anacin) have been shown to displace the breakdown of bilirubin. (6) Even drugs that are safe during pregnancy, when the mother's body is processing them, may not be safe during the early days of lactation, when the baby's liver must break them down on its own.

Age plays a major role in a baby's ability to metabolize drugs. Premature babies with immature digestive systems may have too few liver enzymes and other detoxifying agents to successfully break down and excrete drugs from the body. Many full-term newborns are still not mature enough to metabolize drugs. After one month of age, some babies can effectively handle certain types that they could not assimilate earlier, especially sulfa medications. (7) Older babies, who ingest greater amounts of breastmilk (and possibly drugs), are better prepared to metabolize many of these substances. Later, with the introduction of solids, breastmilk will comprise a smaller part of baby's diet, and the percentage of drug intakes will likewise decrease.

The impact of a drug also hinges on whether it is fat soluble or water soluble. A mother who knows how a particular drug dissolves can adjust her baby's feedings accordingly. Drugs that bind to fats are usually passed along to baby both as a feeding progresses and in the middle part of the day. In other words, the fat content in milk increases as a feeding goes on; it also increases from morning to midday, and then drops off toward evening. A mother taking a fat-soluble medication can reduce the duration of feedings and nurse less at midday; baby can be satisfied with more frequent nursings at other times of the day. Conversely, a drug that is water soluble tends to appear in the earlier skim portion of the milk. In this case, a mother can express a small amount of milk before feeding her baby.

The solubility factor varies among different medications in the same drug family. For example, the barbiturates pentobarbital and secobarbital are present in greater quantity in the fat content of the milk, whereas phenobarbital appears more often in the water-based portion. (8)

Seemingly benign over-the-counter drugs also require caution. Aspirin, a commonly used remedy, has recently recently come under attack for interfering in prostaglandin synthesis during pregnancy: in large doses, aspirin can cause fetal hypertension, amnionic fluid reduction, neonatal bleeding disorders, and delayed onset of labor leading to postterm complications. Although the effects of aspirin on the breastfeeding infant are still under question, a safer option might be Tylenol or, better yet, a nonpharmaceutical approach to pain relief. Any drug may cause problems and is best avoided when possible.

What about Social Drugs?

Studies reveal that tobacco, black tea, alcohol, coffee and other caffeine-based substances, as well as marijuana and other street drugs can negatively affect the quantity or quality of breastmilk. Although some of these substances may produce only minimal alternations, it is difficult, if not impossible, to determine a "safe" limit.

Cigarette smoling, even in small amounts, is contraindicated. To begin with, the smoke inhaled by a baby can cause as many problems as the nicotine ingested in the milk. Babies of mothers who smoke more than 20 cigarettes a day have more vomitting and nausea than those whose mothers do not smoke. [9] In addition, mothers who smoke have decreased levels of milk production, as well as both higher levels of DDT (from the tobacco leaves) and lower levels of vitamin C in their milk; and their children have a greater susceptibility to upper respiratory infections. (10)

Caffeine, one of the most frequently ingested rugs in society, is present not only in coffee, black tea, chocolate, and cola drinks, but also in such over-the-counter medications as stimulants, pain relievers, diuretics, cold remedies, and weight-control aids. Whereas only about 1 percent of the caffeine ingested by a nursing mother appears in her milk, the amount passed on can accumulate in baby's system. (11) Nursing mothers who consume small amounts of caffeine will therefore want to watch for side effects in their babies. The most common responses are wakefulness and hyperactivity--behaviors that are sometimes misdiagnosed as colic. Such side effects can disappear within one week of eliminating caffeine from the diet. (12)

Fortunately, decaffeinated alternatives exist for most caffeine-based substances. However, precautions still need to be taken. Because excessive amounts of some herbal substitutes may be dangerous, it is a good idea to consult an herbalist trained in lactation before selecting a preparation for regular use. (13)

Although alcohol is known to negatively affect the growth and development of a fetus, most studies exploring its impact on the breastfed infant are inconclusive. Small amounts of alcohol may be safe and may even stimulate the let-down reflex. Large amounts, however, can reduce or block the transport of hormones needed to activate this reflex. Alternatives to alcohol are visualization, deep breathing, and other relaxation techniques.

How can a nursing mother begin to assess her situation? She can gain the most security by having her milk tested. When my son Tim was hospitalized as a newborn and the drug I was taking became suspect, I was unwilling to switch to formula without having my milk tested. Fortunately, it was found to contain no traces of medication, and I was able to continue breastfeeding.

In lieu of testing, a mother can combine the best knowledge of her healthcare providers with her own personal experience and a healthy dose of intuition. Her ultimate decision may have to await some trial and error, a change of drugs, and keen observation. Observing "unusual behaviors" in a newborn who has not yet demonstrated many unique personality traits can be a new mother's greatest challenge; nevertheless, it should not be neglected.

The final decision hinges on a weighing of the scales: Do the benefits of treating the mother's medical problem outweigh the possible risks to baby? Are there alternatives to the drug prescribed? For the baby, the health benefits of breastfeeding most often outweigh the risks of the drug. Even in those rare instances in which a safer alternative drug is not available--and in which there is no alternative to drug therapy--with proper planning, breastfeeding may only have to be discontinued temporarily.

Notes

(1) Ruth A. Lawrence, Breastfeeding: A Guide for the Medical Professional, 2nd ed. (St. Louis, MO: C.V. Mosby Company, 1985), p. 254.

(2) Ibid., p. 254.

(3) James T. Wilson, Drugs in Breastmilk (Balgowlah, Australia: Adis Press, 1981).

(4) See Note 1, p. 249.

(5) Henry Vorherr, "Drug Excretion in Breast Milk, "Postgraduate Medicine 56 (1974): 97.

(6) L. Sibai, "How Safe Is Aspirin Use in Pregnancy?" Contemporary Obstetrics and Gynecology 32 (1988): 1.

(7) John H. Clark and W. G. Wilson, "A Sixteen-Day-Old Breastfed Infant with Metabolic Acidosis Caused by Salicylates," Clinical Pediatrics 20 (1981): 53.

(8) See Note 3.

(9) William A. Bowes, Jr., "The Effect of Medications on the Lactating Mother and Her Infant," Clinics in Obstetrics and Gynecology 3 (1980): 1073.

(10) Linda L. Alexander, "Effects of Smoking during Pregnancy and after Birth," Journal of Obstetric, Gynecologic and Neonatal Nursing (May 1987).

(11) See Note 1, p. 261.

(12) Lawrence Rivera-Calimlim, "Drugs in Breastmilk," Drug Therapy 2 (Dec 1977): 20.

(13) For the pros and cons of herbal preparations, see Paul Fleis, MD, "Herbal Remedies for the Breastfeeding Mother," Mothering, no. 48 (Summer 1988): 68-71.

For More Information

Literature

American Academy of Pediatrics Committee on Drugs. "Transfer of Drugs and Other Chemicals into Human Milk," Pediatrics 84, no. 5 (Nov 1989): 924-935. A listing of over 130 pharmacologic and chemical agents transferred into breastmilk and their possible effects, if known, on the infant and on lactation. Address reprint requests to Publications Department, American Academy of Pediatrics, PO Box 927, Elk Grove Village, IL 60009-0927.

Childbirth Education Association of Philadelphia. Counseling the Nursing Mother. WayneM NJ: AveryPublishing Company, 1989.

Eiger, Marvin S., and Sally W. Olds. The Complete Book of Breastfeeding. New York: Workman Publishing, 1986.

Goldfarb, Johanna, and Edith Tibbetts. Breastfeeding Handbook: A Practical Reference for Physicians, Nurses and Other Health Professionals. Hillside, NJ: Enslow Publishers, 1989.

Lawrence, Ruth A. Breastfeeding: A Guide for the Medical Professional, 3rd ed. St. Louis, MO: C. V. Mosby Company, 1989.

Lenette S. Moses (35) is cofounder of Intensive Care Unlimited, a Philadelphia-based parent support organization. She is also a lactation consultant, freelance writer, and graphic artist. Lenette's children are Tim (10), Tad (7), Perrin (3), and Jillian (1-1/2).

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