Firazyr or Icatibant May, With Caution, Be Safe While Breastfeeding

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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New mothers may safely take Firazyr (icatibant; generics available) to treat swelling attacks due to hereditary angioedema (HAE) and continue to breastfeed, provided they wait at least six hours after the last dose before giving their baby breast milk, a case report from Japan suggested.

Icatibant’s safety in women who are pregnant or breastfeeding was not established in the clinical trials that led to the treatment’s approval, as the U.S. Food and Drug Administration noted in its approval label.

When immediate treatment is needed for a swelling attack and a patient cannot wait six or more hours to feed her infant, formula milk should be used, as the woman did in this single case study.

“According to the manufacturer’s instructions, the risk of exposing breastfeeding infants to icatibant is relatively low because systemic absorption through breastmilk is not expected,” the scientists noted, adding that further study is needed.

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The report, “Successful management of hereditary angioedema with icatibant during the postpartum period,” was published as a letter in the Journal of Cutaneous Immunology and Allergy by a team of scientists in Osaka, Japan.

HAE is marked by sudden swelling attacks that can occur anywhere, though most often affect the face, arms, and legs. They can cause pain and discomfort if left untreated, and can be severe, especially if swelling is in the mouth, throat, or intestines. Attacks can occur as often as every week, and their symptoms can last for up to four days.

Treating HAE attacks while breastfeeding

Women are more likely to have more swelling attacks than men, particularly during pregnancy, as estrogen levels rise. They may also become more frequent during breastfeeding, possibly due to high levels of prolactin, the hormone that promotes breast milk production after birth.

Icatibant, whether as Firazyr or as a generic, is used to treat swelling attack symptoms. It is given as a subcutaneous, or under-the-skin, injection, usually into the abdomen. It can be self-injected as soon as a person feels the warning signs of a swelling attack.

The medicine works by blocking the receptors to which bradykinin normally binds. When it binds to its receptors, bradykinin causes blood vessels to widen and fluid to leak into tissues, resulting in swelling. By preventing bradykinin signaling, Firazyr helps to relieve swelling.

While icatibant’s effectiveness is established, the safety of its use by patients who are pregnant or breastfeeding has not been evaluated.

Preclinical studies have shown that small amounts of icatibant can enter a rat’s breast milk, but it remains unknown whether this also holds true for people. Takeda, which markets Firazyr, reported that studies of its properties in the blood show icatibant to be “rapidly and almost completely absorbed” after an injection, and no longer “detected” in blood serum six hours after a dose, the scientists noted. As such, the medicine is not expected to be taken up by the baby’s body through the mother’s breast milk.

“Although breastfeeding has long-term benefits for both a mother and her infant,” they added, “postpartum patients with HAE tend to give up breastfeeding, instead prioritizing on-demand icatibant treatment.”

Researchers reported the case of a Japanese woman who started experiencing repeat episodes of abdominal pain, swelling of the fingers and face, and difficulty breathing at the age of 24.

She was diagnosed with HAE based on her family’s medical history and low activity levels of the C1 inhibitor (C1-INH) protein, which plays a key role in regulating how much fluid leaks into tissues. She also had low levels of C4, a complement system protein that helps mount an immune response against potential threats.

Her treatment included on-demand intravenous (into-the-vein) injections of plasma-derived C1-INH at a hospital.

She became pregnant at age 35, and continued to treat swelling attacks with on-demand injections of plasma-derived C1-INH. After giving birth, she was started on short-term preventive treatment with plasma-derived C1-INH.

This “was the only accepted treatment for pregnant patients with HAE in Japan at that time,” the team wrote.

Four months later, doctors changed her treatment to at-home use of icatibant. When the woman experienced severe limb swelling, she injected the medicine after the last breastfeeding session of the day. Breastfeeding resumed the next day, at least six hours after the injection.

While no reports have examined icatibant use while breastfeeding, including that of Firazyr, studies support its rapid absorption and lack of detection six hours after an injection, the scientists noted.

Icatibant convenient and effective

When the woman experienced abdominal pain or swelling of the face and neck, she injected the medicine immediately, giving the baby formula milk instead of breast milk. She continued to breastfeed her baby for one year throughout on-demand treatment with icatibant.

At age 38, she became pregnant again and resumed on-demand hospital treatment with plasma-derived C1-INH. One month after giving birth, she returned to on-demand treatment with icatibant.

“She has been satisfied with the improvement of symptoms after icatibant administration, which has also significantly improved her quality of life,” the report noted.

Icatibant’s at-home administration was convenient, especially when her swelling attacks were occurring as often as almost every other day.

“In the present case, icatibant was safely used in a lactating patient with HAE. Further evaluation is needed to establish the safety of icatibant for lactating patients with HAE,” the scientists wrote.