Looking at the baby’s eyes filled with desire and trust (Fig. 1, []), every mother would face a dilemma whether to take the medicine or not, to feed the baby or not when the mom gets sick and has to breastfeed the baby. Take it? The drug might pass on to the baby by the breastfeeding and hurt the baby. Not take it? The illness would get worse and the maternal toxins or microorganisms might affect the sweetie through the breastfeeding. What is the correct choice?
Let’s understand how the human milk is produced by the mammary gland first. The basic components of the mammary gland are the alveoli (hollow cavities, a few millimetres large) lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells.
These alveoli join up to form groups known as lobules, and each lobule has a lactiferous duct that drains into openings in the nipple (Fig. 2A, [,]). The lobules are surrounded by blood vessels for the nutrient supply and material exchange with the gland cells (Fig. 2B, []). The milk-secreting cuboidal cells produce and secrete proteins (whey and casein), lipids, and most aqueous constituents of the milk to the alveoli by exocytosis (secreting contents out of cells).
Most of those milk secreting cells are jointed tightly (called tight junctions) and the molecules bigger than 600 Daltons are unlikely to penetrate them from the capillary and interstitial spaces outside the alveoli . This is called as a Blood-Milk Barrier. It releases the infant’s burden to deal with many harmful molecules from maternal circulation (such as methadone, a narcotic drug []).
However, some mechanisms (such as apical transport, transcytosis and paraclelluar pathway) will allow various molecules from the blood to pass through the alveolus epithelial layer to the milk duct (Fig. 2C, ). These molecules include many drugs, immunoglobulin, hormones and growth factors with molecular weight range from hundreds to hundreds of thousands Daltons.
Usually, the amounts of these penetrating molecules in breast milk are small—less than 1% of the maternal intake [,], but certain ones, such as caffeine, their milk level can be as high as 63% of the blood concentration []! Even larger particles, such as immune cells and bacteria (they are composed of millions of big molecules), have their way to migrate from the mother’s blood into the breast milk [1, ].
These mechanisms provide the infant a passive immune (such as immune cells and IgA) against diseases, but at the same time, they are also potential risks as they can introduce mother’s harmful molecules to the baby.
So what molecules have been found in breast milk from the maternal circulation? Table-1 below shows just a few examples of many molecules that were reported in the breast milk, everything from good molecules (IgA) to bad (alcohol); from small molecules (alcohol, 121D) to big (IgE, 200KD); from food constituent (caffeine) to synthesized drug (aspirin), etc. For more information about the molecules that are reported in the breast milk, please refer to the reference [6,]. Almost all drug molecules in maternal circulation might get into the breast milk [].
The most important determinant of the drug into the milk is the maternal plasma drug levels. When the drug level rises in maternal plasma, its level in milk also increased, almost without exception . Some drugs (such as erythromycin, thiouracil) can have higher milk concentration than serum concentration .
As for the effect of the drug on the breastfeeding infants, it mainly depends on the properties of the drug itself. Some drugs are safe for the baby at the breast milk level, and some drugs can cause adverse or very serious reactions, such as pathological jaundice, deafness, cyanosis, hearing loss, vomiting and damages of liver and kidney functions .
Table-1. Molecules in Breast Milk.
Functions, influences or comments
|Rapidly equilibrates between the plasma and milk compartments .|
180 D []
|When orally taking 975 mg of aspirin, maximal in serum at 2.25 hours (10.8 mg/dL) and in milk at 3.00 hours (1.0 mg/dL). Milk:serum ratios ranged up to 0.08 .|
194 D []
|Caffeine concentrations peaked at 5.50 hours in serum (2.14 µg/mL) and at 2.00 hours in milk (1.15 µg/mL) during a period of steady coffee drinking by the mother. Milk:serum ratios ranged up to 0.63 .|
|An antibiotic, 500 mg, p.o. once leads the breast milk concentration to 9.1 µmol/L after 4 hours and keep for 12h hours at this level []. Ciprofloxacin should not be used in infants as they have not developed sufficient enzymes to metabolize the drug [].|
|IgA is presented in breast milk, providing a passive immune protection for the infant against many invading pathogens [].|
|The mother caught a virus and produced the antibody IgE in the blood. The presence of IgE in breast milk and infant serum suggests that the antibodies are transmitted in breast milk and may provide protective responses in nursing children [].|
contains millions of big molecules
|A mother with a streptococcus infection would pass the bacterium to the child via breastmilk .|
Now, let’s look at the situations on the Traditional Chinese Medicine (TCM) herbs. The reason why people question the safety of TCM herbs on breastfeeding is due to the lack of the information from studies on that issue. People who worry this issue may have the concern from the saying that “It is more or less toxic as long as it is a medicine” []. People who think herbs are safe may have the logic that the conventional TCM formulas have been used for hundreds-thousands of years without acute side effect if used correctly, or else they would be modified or eliminated.
The major difference of western drug medicine and traditional Chinese herbal medicine is the use of quantified known molecules. Although many of major constituents of TCM herbs have been studied, it is too hard to track hundreds of molecules in an herb or a formula on their reactions and metabolisms in the blood and breast milk.
Even many of those TCM herbs that are commonly thought to be avoided while in breastfeeding (such as Da Huang), might be a lack of scientific evidence (Table-2). Since there is a lack of scientific study to show whether the constituents of an herb/formula enter the breast milk and whether those breast milk affect the infant’s metabolisms, whatever people conclude on the issue of TCM herbs and breastfeeding is only a speculation, based on the knowledge (such as the molecular weight) of other molecules in the breast milk.
So, to feed or not to feed? That is still the question. However, from the logic of the above blood-milk barrier mechanisms, the known drug molecules in milk and the molecules in TCM herbs, what we should keep in mind on this issue are:
- In theory, there is a possibility that all molecules from maternal circulation can pass the blood-milk barrier and get into the breast milk . Therefore, the molecules that may affect maternal metabolisms may affect the infant metabolisms too via breastfeeding.
- Fortunately, many molecules show lower milk concentrations – less than 1% of the maternal intake. This mechanism may be the basis to ensure the possible safety of taking some herbs/formulas while breastfeeding, but it is still better to ask the doctor or search the information on the constituents of the herb/formula before taking them while breastfeeding.
- If taking TCM herbs while breastfeeding, the mother should watch the baby more closely for any abnormality, such as inactive, rash, diarrhea, vomiting, fever, jaundice, etc., in case any unsure chemicals from the herb cause the problem.
- The drug molecule may reach the peak level in plasma 60-120 minutes after orally taking the TCM herbs, while it may take another 30 – 120 minutes to reach the milk peak after the plasma peak . Try to avoid the drug peak time in milk (2-4 hours after taking herbs) to feed the baby. It is better to collect the breast milk 6-8 hours after taking herbs and save it for the baby’s needs to minimize the herbal influence to the baby.
Table-2. TCM Herbs/Formula That Are Commonly Thought to Be Avoided While on Breastfeeding , Their Major Constituent, Reports in Milk and Influences to Infants.
Breast Milk & Infant Influence
|Constipation||Fan Xie Ye (番泻叶, Senna plus Plantago ovata as laxative)||Rhein (MW=284), possible binding as monoglucuronide and monosulfate .||0.017% of the sennoside intake (calculated as rhein) was excreted in breast milk. The amount of rhein transmitted to the infant is therefore 0.3% of the rhein intake of the mother. None of the breast-fed infants had an abnormal stool consistency [].|
|Constipation, stomatitis, oral ulcer||Da Huang (大黄)||Chrysophanol (MW*=254), Emodin (MW=270) []||Not found in PubMed and Baidu.com in Chinese**.|
|Aphthae||Sheng Ma (升麻)||(1) Cimicifugin (MW=306), (2) salicylic acid (MW=138) []||(1) Not found in PubMed and Baidu.com in Chinese. (2) 0.4% of plasma concentration in milk []. When ingested, salicylic acid has a possible ototoxicity and mortality [].|
|Rheumatic arthralgia||Hu Ji Sheng (槲寄生)||Oleanic acid (MW=457), Rhamnazin (MW=330) [],||Not found in PubMed and Baidu.com in Chinese.|
|Upper respiratory tract infection||Huang Qin (黄芩)||Baicalein (MW=270), baicalin (MW=446) []||Not found in PubMed and Baidu.com in Chinese.|
|Sore throat||Bo He (薄荷)||Menthol (MW=156), Menthone (MW=154) []||Not found in PubMed and Baidu.com in Chinese.|
|Agalactia []||Lou Lu (漏芦)||Limonene (MW=136), echinopsine (MW=159) []||Not found in PubMed and Baidu.com in Chinese.|
|Indigestion||Mai Ya (麦芽)||Hordenine (MW=165) []||Not found in PubMed and Baidu.com in Chinese.|
|Chronic hepatitis, cirrhosis||Xiao Yao San (逍遥散)||Saikosapoins (MW=781), humulene (MW=204) []||Not found in PubMed and Baidu.com in Chinese.|
*MW: Molecular weight; the numbers are from Google search (Wikipedia).
** “Not found in PubMed and Baidu.com in Chinese”: Not found in the first several pages of PubMed and Baidu.com in Chinese when using the key words of the major constituent and breast milk/breastfeeding. It indicates that the related issue is not collected by the well-known scientific database in English or not searchable by the biggest search engine in Chinese. Either the issue is not well documented, or the issue is not important enough for a study.
 Lauren M. Jansson et al: Concentrations of Methadone in Breast Milk and Plasma in the Immediate Perinatal Period. J Hum Lact, May 2007; 23: 184 – 190.
 David N. Bailey et al: A Study of Salicylate and Caffeine Excretion in the Breast Milk of Two Nursing Mothers. J Anal Toxicol, Mar 1982; 6: 64 – 68.
 Riccardo Davanzo et al: To Feed or Not to Feed?: Case Presentation and Best Practice Guidance for Human Milk Feeding and Group B Streptococcus in Developed Countries. J Hum Lact, Mar 2013; 10.1177/0890334413480427.
 Ralph E. Kauffman et al: The Transfer of Drugs and Other Chemicals into Human Breast Milk. Pediatrics, Sep 1983; 72: 375 – 383.
 DL Cover and BA Mueller: Ciprofloxacin penetration into human breast milk: a case report. Ann. Pharmacother., Jul 1990; 24: 703 – 704.
 Cheryl A. Lovelady et al: Effect of Exercise on Immunologic Factors in Breast Milk. Pediatrics, Feb 2003; 111: e148 – e152.
 Tamar A. Smith-Norowitz et al: Detection of IgE Anti-Parvovirus Antibodies in Human Breast Milk. Ann. Clin. Lab. Sci., Jan 2008; 38: 168 – 173.
 P Faber and A Strenge-Hesse: [Senna-containing laxatives: excretion in the breast milk?]. Geburtshilfe Frauenheilkd, Nov 1989; 49(11): 958-62.
 JW Findlay et al: Analgesic drugs in breast milk and plasma. Clin Pharmacol Ther, May 1981; 29(5): 625-33.