I need to take medicine during breastfeeding. Which one is safer? Can I still breastfeed?

Author: Zhang Lan, Chief Pharmacist, Shanghai Maternal and Child Health Center

Reviewer: Xie Hongjuan, Chief Pharmacist, Shanghai First Maternity and Infant Health Care Hospital

Fan Chongchun, deputy chief nurse of Shanghai Maternal and Child Health Center

Breast milk is the most ideal natural food for babies. However, during breastfeeding, mothers will inevitably get sick and need to take medicine. So, can you continue breastfeeding after taking medicine during breastfeeding?

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Effects of medication during lactation on infants

Drugs may enter the infant's body through breast milk. Although it is generally believed that the drug concentration in breast milk is not high enough to have adverse effects on infants, for drugs that are easily absorbed by the gastrointestinal tract, even if the drug concentration in breast milk is low, infants may absorb a considerable dose of the drug, because infants can generally suck about 800 to 1000 ml of breast milk every day. Therefore, when taking drug treatment during breastfeeding, you should try to do the following:

1. Give priority to drugs with short half-lives. These drugs can be quickly cleared from maternal plasma, thereby reducing drug exposure in breast milk. The half-life of a drug is an important factor in determining whether it can be safely used during breastfeeding. Information on the half-life can be found in the "Pharmacokinetics" section of the drug instructions.

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2. Molecular weight (MW) is an important determining factor for drugs to enter breast milk. Try to choose drugs with large molecular weight. Drugs with small molecular weight (<800) can penetrate the small membrane pores between mammary epithelial cells, while drugs with large molecular weight must dissolve in the lipid membrane of epithelial cells to pass through the cell membrane, which may greatly reduce the drug concentration in breast milk.

3. Try to choose drugs with high protein binding rate. In maternal plasma, drugs may be bound to proteins or free in plasma. The free part will be transported to breast milk, while the bound part will remain in the human circulation. Therefore, choosing drugs with high protein binding rate can help reduce the amount of drugs in breast milk.

4. Avoid using drugs that easily enter the brain tissue. As the blood drug concentration increases, such drugs are more likely to enter the brain tissue. For example, most anti-epileptic drugs (such as carbamazepine, sodium valproate, etc.) should be avoided during breastfeeding.

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In addition to half-life (t1/2), relative infant dose (RID) and lactation risk level (LRC) are also commonly used indicators for assessing the risk of drug use during lactation.

The relative infant dose is the ratio of the dose an infant receives from breast milk to the dose a breastfeeding woman takes. It is generally believed that a relative infant dose of less than 10% is safe during breastfeeding, and the relative infant dose of most drugs is less than 1%.

The breastfeeding risk level is divided into 5 levels from L1 to L5. Try to choose drugs with a breastfeeding risk level of L1 to L2, which are safe during breastfeeding.

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The following are some commonly used medications for breastfeeding women for your reference.

Commonly used drugs for breastfeeding women

Key points about breastfeeding and medication

1. Avoid the peak period of drug concentration: In order to reduce the impact of drugs on the baby, when taking drugs during breastfeeding, the breastfeeding time should avoid the peak period of drug concentration in breast milk. The drug can be taken 30 to 60 minutes after breastfeeding, and the next breastfeeding time can be appropriately delayed so that most of the drug can be cleared from the mother's blood, which is beneficial for the baby to avoid the peak period of drug concentration when sucking breast milk.

2. Use non-essential drugs with caution: Traditional Chinese medicine, high-dose vitamins, special nutritional supplements, etc. also have certain risks and should be avoided when not necessary. When using drugs during breastfeeding, they should be used under the guidance of clinical physicians and pharmacists, and prohibited drugs should be avoided.

3. Comprehensive assessment of drug risks: A comprehensive assessment should be conducted based on the drug's dosage, half-life, molecular weight, protein binding rate, relative infant dose, and breastfeeding risk level, and the most suitable drug should be selected after weighing the pros and cons.

4. Take medication as directed by your doctor: Be sure to take medication as directed by your doctor and do not miss, stop taking, or reduce the dosage on your own.

References:

[1] Li Jun, Clinical Pharmacology Study Guide and Exercises, 1st edition, Beijing: People's Medical Publishing House, 2013: 978-7-117-17888

[2] Thomas W. Hale, Hillary E. Rowe (ed.), Xin Huawen, Yang Yong (translator), 17th edition, Shanghai World Book Publishing Company, 2019: 09-2017-798