Data Is Lacking on Safety of MS Treatments During Breastfeeding

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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There is minimal data available on the safety of most disease-modifying therapies for multiple sclerosis (MS) when used during breastfeeding, a new review indicates.

The study “Disease-Modifying Drugs and Breastfeeding in Multiple Sclerosis: A Narrative Literature Review,” was published in Frontiers in Neurology.

Disease-modifying therapies, or DMTs, are medications that can slow the progression of MS — for example, by reducing the risk of disease relapses and worsening disability. More than a dozen DMTs have been widely approved to treat MS.

MS predominantly affects females, and it usually develops during early adulthood. Many MS patients choose to become pregnant and a wealth of data has shown that MS itself does not increase the risk of complications during pregnancy.

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However, some DMTs may pose risks to the developing fetus if taken during pregnancy. Similarly, some medications can be transferred into breast milk, which could potentially harm newborns if they are being breastfed.

This poses a dilemma for patients who have to weigh the potential harm to their child against the benefits of treatment to control their disease. Further complicating matters, clinical trials that test new MS therapies generally exclude patients who are pregnant or breastfeeding for ethical reasons, so in many cases there is little information about whether DMTs can be safely used under these circumstances.

Scientists in Italy conducted a review of the available scientific literature concerning the use of DMTs for MS while breastfeeding.

For some older DMTs, specifically interferon therapies and glatiramer acetate (sold as Copaxone, among others), some evidence shows these medicines can safely be used while breastfeeding as available data indicate that little of the medicine is excreted in human breast milk. Some small studies have found no notable safety issues in infants breastfed during treatment.

However, the research team noted that, even for these relatively established therapies, there are some inconsistencies regarding their approval. For example, in the European Union, the labels for the interferon beta-1a therapies Avonex and Rebif state that these medicines are negligibly excreted in human breast milk and that they may be used while breastfeeding. But in the U.S., labels for the same therapies advise caution when treating breastfeeding patients because it’s not known if the medicines are excreted in breast milk.

For most other DMTs, the researchers emphasized that there is little or no published data on their safety during breastfeeding. These include: dimethyl fumarate (marketed as Tecfidera, among others); teriflunomide (marketed as Aubagio, among others); natalizumab (marketed as Tysabri, among others); Mavenclad (cladribine tablets); Lemtrada (alemtuzumab); sphingosine-1-phosphate (S1P) receptor modulators such as Gilenya (fingolimod), Mayzent (siponimod), and Zeposia (ozanimod); and anti-CD20 therapies such as Ocrevus (ocrelizumab) and Kesimpta (ofatumumab).

In most cases, these DMT labels recommend that decisions about whether to use the therapies during lactation should be made on a case-by-case basis, weighing the potential risks to the infant against potential benefits for the patient.

“At present, there is limited information for most DMTs regarding human milk transfer and effects on the breastfed infant. Consequently, very few DMTs are explicitly licensed for use during breastfeeding and a case-by-case decision is recommended for most of them,” the researchers wrote.

“To help the clinician in providing a recommendation for any treatment resumption after delivery, it seems reasonable to check for disease activity shortly after pregnancy, with a brain and spine MRI. The management should be discussed with the mother,” the research team said, noting that more research was needed about these treatments’ effect on breastfeeding.

“Post-marketing clinical registries and prospective clinical trials would be particularly helpful in achieving this goal,” they wrote.

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