Does the addition of a small amount of medication to the mother’s milk make breastfeeding more hazardous than formula feeding?

The answer is almost always: Almost never.

Breastfeeding with a little drug in the milk is almost always safer. In other words, being careful means continuing breastfeeding, not stopping.

Remember that stopping breastfeeding for a week may result in permanent weaning since the baby may then not take the breast again. On the other hand, it should be taken into consideration that some babies may refuse to take the bottle completely, so that the advice to stop is not only wrong, but often impractical as well. On top of that it is easy to advise the mother to pump her milk while the baby is not breastfeeding, but this is not always easy in practice and the mother may end up painfully engorged.

Breastfeeding and Maternal Medication

Most drugs appear in the milk, but usually only in tiny amounts. Although a very few drugs may still cause problems for infants even in tiny doses, this is not the case for the vast majority.

Nursing mothers who are told they must stop breastfeeding because of a certain drug should ask the physician to make sure of this by checking with reliable sources and/or prescribing an alternative safe medication.

In this day and age, it is rarely a problem to find a safe alternative. If the prescribing physician is not flexible, the mother should seek another opinion, but not stop breastfeeding.

Why do most drugs appear in the milk in only small amounts? Because what gets into the milk depends on the concentration in the mother’s blood and the concentration in the mother’s blood is often measured in micro- or even nano-grams per millilitre (millionths or billionths of a gram), whereas the mother takes the drug in milligrams (thousandths of grams) or even grams. Furthermore, not all the drug in the mother’s blood can get into the milk. Only the drug that is not attached to protein in the mother’s blood can get into the milk. Many drugs are almost completely attached to protein in the mother’s blood. Thus, the baby is not getting amounts of drug similar to the mother’s intake, but almost always, much much less on a weight basis. For example, in one study with paroxetine (Paxil), the baby got less than 0.3% of the drug for each kilogram of his weight than the mother did (the mother got over 300 micrograms per kg per day, whereas the baby got about 1 microgram per kg per day).

Most drugs are safe if:

• They are commonly prescribed for infants. The amount the baby would get through the milk is much less than he would get if given directly.
• They are considered safe in pregnancy. This is not always true, since during the pregnancy, the mother’s body is helping the baby’s get rid of drug. Thus it is theoretically possible that toxic accumulation of the drug might occur during breastfeeding when it wouldn’t during pregnancy (though this is probably rare). However, if the concern is for the baby’s merely getting exposed to a drug, say an antidepressant, then the baby is getting exposed to much more drug at a more sensitive time during pregnancy than during breastfeeding.
• They are not absorbed from the stomach or intestines. These include many, but not all, drugs given by injection. Examples are gentamicin (and other drugs in this family of antibiotics), heparin, interferon, local anaesthetics, omperazole.
• They are not excreted into the milk. Some drugs are just too big to get into the milk. Examples are heparin, interferon, insulin.

The following are a few commonly used drugs considered safe during breastfeeding:

• Acetaminophen (Tylenol, Tempra), alcohol (in reasonable amounts), aspirin (in usual doses, for short periods). Most antiepileptic medications, most antihypertensive medications, tetracycline, codeine, nonsteroidal antiinflammatory medications (such as ibuprofin), prednisone, thyroxin, propylthiourocil (PTU), warfarin, tricyclic antidepressants, sertraline (Zoloft), paroxetine (Paxil), other antidepressants, metronidazole (Flagyl), omperazole (Losec), Nix, Kwellada.
   
  Note: Though generally safe, fluoxetine (Prozac) has a very long half life (stays in the body for a long time). Thus, a baby born to a mother on this drug during the pregnancy, will have large amounts in his body, and even the small amount added during breastfeeding may result in significant accumulation and side effects. These are rare, but have happened. There are two options that you might consider:
   
  
  1. Stop the fluoxetine (Prozac) for the last 4 to 8 weeks of your pregnancy. In this way, you will eliminate the drug from your body and so will the baby. Once the baby is born, he will be free of drug and the small amounts in the milk will not usually cause problems and you can restart the fluoxetine (Prozac).
  2. If it is not possible to stop fluoxetine (Prozac) during your pregnancy, consider changing to another drug which does not get into the milk in significant amounts once the baby is born. Two good choices are sertraline (Zoloft) and paroxetine (Paxil).

  
  

• Medications applied to the skin, inhaled (for example, drugs for asthma) or applied to the eyes or nose are almost always safe for breastfeeding.
   
• Drugs for local or regional anaesthesia are not absorbed from the baby’s stomach and are safe. Drugs for general anaesthesia will get into the milk in only tiny amounts (like all drugs) and are extremely unlikely to cause any effects on your baby. They usually have very short half lives and are eliminated extremely rapidly from your body. You can breastfeed as soon as you are awake and up to it.
   
• Immunizations given to the mother do not require her to stop breastfeeding. On the contrary, the immunization will help the baby develop immunity to that immunization, if anything gets into the milk. In fact, most of the time nothing does get into the milk, except, possibly some of the live virus immunizations, such as German Measles. And that’s good, not bad.
   
• X-rays and scans. Ordinary X-rays do not require a mother to stop breastfeeding even when used with contrast (example, intravenous pyelogram). The reason is that the material does not get into the milk, and even if it did it would not be absorbed by the baby. The same is true for CT scans and MRI scans. You do not have to stop for even a second.

What about radioactive scans?

We do not want babies to get radioactivity, but we rarely hesitate to do radioactive scans on them. When a mother gets a lung scan, or lymphangiogram with radioactive material, or a bone scan, it is usually done with technetium (though other materials are possible). Technetium has a half life (the length of time it takes for 1/2 of all the drug to leave the body) of 6 hours, which means that after 5 half lives it will be gone from the mother’s body. Thus, 30 hours after injection all of it will be gone and the mother can nurse her baby without concern about his getting radiation. But does all the radioactivity need be gone? After 12 hours, 75% of the technetium is gone, and the concentration in the milk very low. I think that after most radioactive scans, the mother can continue breastfeeding, but if she and her physician are truly concerned, waiting 2 half lives is enough, for a material such as technetium. Note that if the mother is getting the scan during the first few days after the baby’s birth, the baby will get much less because the baby gets much less milk during this time. During this early period, I believe no interruption of breastfeeding is necessary or desirable. Colostrum is desirable for the baby.

If you decide that interruption of breastfeeding is the best course to follow, then express milk for several days in advance (if you have advance warning about the test). Only occasionally is a radioactive scan that urgent that it cannot be delayed for a few days.

Thyroid scans are different. Radioactive iodine is concentrated in milk and will be ingested by the baby and it will go to his thyroid where it will stay for a long time. This is definitely of concern. So, the mother will have to stop breastfeeding? No, because often the test does not need to be done. Differentiating postpartum thyroiditis from Graves’ Disease (the most common reason for doing the scan in nursing mothers) does not require a thyroid scan. Get more information from the clinic. If a scan needs to be done, it is possible to do a thyroid scan with technetium.

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