Medication decisions during breastfeeding rarely come down to a simple question of whether a drug passes into human milk.
Clinicians may also need to consider how much medication reaches the infant, whether the drug survives the infant’s gastrointestinal tract, the infant’s age and health, maternal dosing, possible effects on milk production, and the risks of leaving the mother’s condition untreated.
That more nuanced approach to lactation pharmacology is at the center of the upcoming Hale’s Medications & Mothers’ Milk 2027–2028, according to author Kaytlin Krutsch, PhD, PharmD, MBA, BCPS, director of the InfantRisk Center of Excellence and associate professor of obstetrics and gynecology at Texas Tech University Health Sciences Center School of Medicine.
During a recent Springer Publishing webinar, “What Changed and Why It Matters: The New Hale’s,” Krutsch walked clinicians through key changes in the new edition and discussed how evolving evidence is changing the assessment of medications during breastfeeding.
Medication Transfer Into Milk Is Only Part of the Question
One of the biggest changes in the new edition comes before clinicians even reach the individual drug monographs.
Krutsch substantially revised the introductory material to provide a broader framework for evaluating medications during lactation.
The amount of medication that transfers from maternal plasma into milk matters, but it does not determine infant exposure or risk on its own. Clinicians may also need to consider the relative infant dose, or RID; whether the drug remains stable after entering the infant’s gastrointestinal tract; how much the infant may absorb; and how well the infant may tolerate that exposure.
The new edition includes a graphic illustrating the movement of a drug from maternal plasma into milk and then into the infant, along with factors that influence clinical interpretation.
The assessment also needs to account for the mother’s treatment needs.
“We talk about medications being a barrier to breastfeeding,” Krutsch said. “But I think those of us all in practice are pretty aware that breastfeeding can be a barrier to medications.”
Fear about exposing an infant to medication can sometimes lead patients to avoid treatment even when clinicians are relatively comfortable with the medication, she said.
More Data Are Changing Lactation Risk Categories
Clinicians also have considerably more research to interpret than they once did.
Krutsch described an “explosion of information” about medications and breastfeeding, noting that a PubMed search she conducted showed a steep increase in published literature over the past several decades.
Not all of that research provides usable lactation data, she cautioned. But enough new evidence is accumulating to change how some medications are classified.
In the 2027–2028 edition, 88 drugs had changes to their lactation risk categories, Krutsch said. About half moved to a category indicating less concern, while 15 moved to a category indicating greater caution. The L2 category saw particularly notable growth as more evidence became available.
Hale’s uses five lactation risk categories, ranging from L1 (Compatible) to L5 (Hazardous), with the classifications reflecting the available evidence and potential risk to a breastfed infant.
But clinicians should not treat the category as the final answer.
“We just don’t want to just look at a lactation risk category and call it a day,” Krutsch said.
Contraceptives Get a More Nuanced Treatment
Contraception is one area where that additional nuance is particularly visible.
Previous editions grouped hormonal contraceptives under a single monograph. The new edition separates them into three: nonhormonal contraceptives, progestin-only contraceptives, and combined hormonal contraceptives.
Combined hormonal contraceptives are classified as L3 and receive additional discussion about their potential effects on milk supply.
Krutsch said that, on average, she does not believe most patients experience a reduction in milk production from combined hormonal contraceptives. But averages do not capture every patient’s experience.
“I don’t want to just say, you know, no combined hormonal contraceptives don’t impact milk supply,” she said. “I really am trying to be respectful of the moms that really do feel like they have a change.”
Atomoxetine Moves From L4 to L2
Some classifications changed substantially as new evidence became available.
Atomoxetine, a nonstimulant medication used to treat ADHD and sold under the brand name Strattera, moved from L4 to L2.
Krutsch discussed an InfantRisk Center study that found minimal transfer of atomoxetine into human milk. The study included 10 lactating participants taking 40 to 100 mg daily and calculated a mean RID of 0.19%, with no adverse effects reported in the breastfed infants.
Citalopram also moved from L3 to L2, while escitalopram is L2.
Krutsch emphasized that differences in RID or lactation risk classification should not automatically prompt clinicians to switch a patient from an SSRI that is working.
“Whichever SSRI is the one that works is the one that I think that you should go with there,” she said.
New Iodine-131 Research Highlights the Potential of Individualized Assessment
Krutsch also highlighted new research examining whether individualized radiation measurements could eventually help refine recommendations involving iodine-131.
She discussed a recent case report involving a woman who received therapeutic sodium iodide I-131 for thyroid cancer. Researchers measured radioactivity in expressed breast milk and used individualized dosimetry to model potential infant exposure.
In this case, the analysis found that resuming breastfeeding nine to 10 days after treatment could keep estimated infant exposure below one radiation safety threshold. Using a stricter criterion based on radioactivity in the milk, however, produced a substantially longer estimate of 51 days.
The finding is preliminary and does not change current guidance. LactMed continues to state that sodium iodide I-131 is generally contraindicated during lactation and that breastfeeding should be permanently discontinued for the current child after therapeutic administration.
Still, Krutsch pointed to the case as an example of how individualized dosimetry may provide additional information as researchers continue to study radiation exposure during lactation.
More Evidence Is Emerging on Monoclonal Antibodies
The expanding use of monoclonal antibodies has created another challenge for clinicians counseling breastfeeding patients.
The new edition includes individual monographs for monoclonal antibodies rather than relying primarily on broader tables.
Krutsch explained that monoclonal antibodies can enter human milk, but they are large proteins and milk transfer tends to be relatively low. Proteins reaching the infant’s gastrointestinal tract are also generally broken down during digestion.
More infant outcomes data have accumulated as these medications have become more widely used.
“I’m less worried about monoclonals than, you know, when they first came out,” Krutsch said.
Individual drugs still require assessment, however, because monoclonal antibodies act on different biological targets.
An L4 Medication Does Not Automatically Mean Stop Breastfeeding
One of the webinar’s most practical discussions came during the Q&A, when clinicians asked how they should approach L3, L4 and L5 medications.
Krutsch emphasized that an L4 classification does not automatically mean breastfeeding must stop.
She used lithium as an example of a medication for which breastfeeding may be a reasonable option in some circumstances when the patient wants to continue, the pediatrician is involved, and appropriate monitoring can be performed.
Instead, an L4 classification should signal the need for closer review of the medication and dose, available evidence, the infant’s health and age, monitoring options, alternative treatments, maternal health needs, and the patient’s preferences.
“Look at the patient in front of you, look at their infant, look at what they want,” Krutsch said.
New Summaries Are Designed for Faster Clinical Use
The growing evidence base has created another practical problem: some drug monographs have become long.
To make them easier to use, the 2027–2028 edition introduces short “TL;DR” summaries for some longer monographs, giving clinicians a quick takeaway before the full evidence review.
Several appendices have also been expanded or revised, with information on contraceptives and radioactive medications, drugs and conditions that may alter the appearance of human milk, medications that may affect milk flavor, and medications that can interfere with readings from Miris human milk analyzers.
Medication Decisions Are Becoming More Individualized
One theme connected many of the changes Krutsch discussed: Medication decisions during breastfeeding cannot always be reduced to a single number or risk category.
Evidence matters, but so do dose, infant exposure, maternal health, the infant’s clinical status, available monitoring, treatment alternatives, and the patient’s goals. Sometimes, the evidence simply isn’t there yet.
Krutsch encouraged clinicians and breastfeeding patients to participate in lactation research when possible. The InfantRisk Center maintains a human milk biorepository and recruits participants for studies involving medications for which lactation data remain limited.
As that evidence base grows, recommendations and risk classifications will continue to evolve.
Hale’s Medications & Mothers’ Milk 2027–2028 incorporates updated lactation pharmacology evidence and expanded clinical guidance to help healthcare professionals navigate those decisions.
Clinicians can also watch Krutsch’s full Springer Publishing webinar, “What Changed and Why It Matters: The New Hale’s,” for a deeper discussion of the new edition, individual medications, and questions raised by healthcare professionals during the session.
Learn more: Hale’s Medications & Mothers’ Milk 2027–2028 from Springer Publishing.
Watch on demand: What Changed and Why It Matters: The New Hale’s, Live with Dr. Kaytlin Krutsch.
- Medications and Breastfeeding: What’s Changing in the New Hale’s - September 18, 2026
