Centrum Nauki o Laktacji im. ANNY OSLISLO

Lactational Medications’ Lexicon

Do you have to give a medication to breastfeeding mother?

Do you have any concerns? Are you looking for reliable sources? The best of lexicons we known is this written by Professor Thomas W. Hale: Medications and mothers’ milk, actualized every two years. We are using this lexicon for many years to chose precisely medications doses and proper rout of administration for our patients. Actually, its 18th edition issued in 2019 by Springer Publishing Co. This 2019 edition has been extensively revised, and now includes 39 completely new and 331 updated medications, and state-of-the-art coverage of multiple diseases, vaccines, and syndromes. It addresses the use of radiopharmaceuticals, chemotherapeutic agents, and vaccines in breastfeeding mothers, and covers adult concerns, methods of reducing risk to infants, and infant monitoring.

You may also order lexicon in OUR SHOP.  You can also use the Hale’s site https://www.infantrisk.com/

Professor Hale has created risk categories for use of medications during lactation period (Hale’s Lactation Risk Categories) that help medical practitioners make decisions in treatment. In order to enable Polish medical doctors and patients have a quick insight into his risk categories we provide you a list of drugs sorted alphabetically due to international nomenclature, concerning a lactation risk category for each medication according to Prof. Hale’s categories and concerning FDA (Food and Drug Administration) drugs’ pregnancy risk. Wider information on drug’s properties, the time after which it passes into milk, the impact on the child in specific doses based on clinical trials, and many other – you will find in Medications and mothers’ milk by Prof. Thomas W. Hale. Our short lexicon was made with the approval and cooperation of Prof. T. Hale (Thank you!).


Lactational Medications’ Lexicon


Prof. Hale`s Lactation Risk Categories:

L1 „safest”

This group consists of medications that were taken by a large number of mothers during lactation period without any adverse effect in infants. There were clinical trials performed on breastfeeding mothers with use of drugs form this group, that showed neither risk for infants nor possibility of remote adverse effects. This group includes also medicinal products orally unavailable for children.

L2 „safer”

This group includes medications that were taken by a limited number of breastfeeding mothers that showed no adverse effects in their infants. It consists also of drugs which have very little possibility to show adverse effects on breastfed children.

L3 „probably safe”

There are no controlled trials on breastfeeding mothers concerning this medications, however, the risk of adverse effects in breastfed children is possible. It concerns also those drugs, for which control trials revealed only minimal unthreatening adverse effects. Medications from this group should be administered only if possible benefits outweighs the risk for breastfeed children. Moreover, all new medications without certain controlled trials are included into this group automatically, which is irrespective of how safe they may be for breastfed children.

L4 „probably hazardous”

For medications included into this group are available proves on their hazardous effect on breastfed children or mother’s milk, however benefits of their use in breastfeeding mothers may be acceptable despite existing risk for children (e.g. if drug is administered in life threatening situation or if there is a risk of serious disease, in situation, when there is no possibility to use other, safer medication, or it is ineffective).

L5 „hazardous”

There were clinical trials on group of breastfeeding mothers that showed significant and documented risk for children based on experiences on humans. This group is also consisted of medications of high risk of adverse effects in children. The risk of use of this drugs in breastfeeding mothers significantly outweighs any possible benefit of breastfeeding. This medications are contraindicated in breastfeeding mothers.

FDA risk categories for use of medications during pregnancy

The risk categories of medications administered during pregnancy were specified for almost all medical products. Nowadays, producers provide detailed information on a risk for fetus that results from taking each medication in pregnancy. In presented list, some medications are classified to more than one risk group. That results from a specific, often different effect on fetus that depends on a pregnancy period.

A – This group is consisted of medications with available clinical trials that showed no risk for fetus when administered during first trimester, or there are no proves for existence of such risk during last two trimesters and the possibility of adverse effect seem to be unlikely.

B – Studies on animals did not show risk for fetus, however, medications included into this group have no clinical trials on pregnant woman. This group is also consisted of medical products for which studies showed some adverse effects on fetus in animal models (other than decrease in fertility), that was not confirmed in clinical trials on pregnant woman in first trimester, and there are no proves for risk in last two trimesters.

C – This group is consisted of medications, for which the adverse effects on fetus were observed in clinical trials (teratogenicity, embryotoxicity, or other) and for which there are no clinical trials on pregnant woman available or trials on animal model or in humans are unavailable. A medical product classified into this group should be administered  when benefits outweighs the risk.

D – For medications from this group there are proves for their hazardous effect on human fetus, but their usage in pregnant woman is acceptable despite the risk (e.g. if there is necessity to administer a drug in life threatening situation or in serious disease, when there is no possibility to use safer drug, or such product is ineffective).

X – This group includes medications with clinical trials on animals or humans that showed fetal abnormalities and/or there are proves of risk for fetus and the risk of usage of this medications in pregnant woman outweighs any possible benefit. Drugs from this group are contraindicated in pregnant woman or may become pregnant.


  1. – dose

duże D. – in high doses

now. – in neonatal period

wcześniak –  in first few weeks in premature infants’ mothers

trym. – trimester

przewl. – during chronic treatment

późno – in late period of lactation

mc – months

lecz. – in therapeutic doses

miejsc. – during topical treatment

p.o. – during oral intake

i.v. – during intravenous treatment

p.v. – during per vaginal treatment

narkot. – used as a narcotic agent