Asthma Home > Zyflo and Pregnancy

In previous animal studies involving Zyflo and pregnancy, the drug increased the risk of skeletal birth defects and low birth rate, and also caused some birth defects (including cleft palate). However, a healthcare provider can still prescribe the medication to a pregnant woman if he or she believes that the benefits outweigh the possible risks to the unborn child. If you are taking Zyflo and pregnancy occurs, let your healthcare provider know.

In February 2008, the manufacturer of Zyflo announced that it has discontinued making this product. The manufacturer stated that since the longer-acting version, Zyflo CR, became available in 2007, use of immediate-release Zyflo declined significantly. Zyflo CR will still be available.

Is Zyflo Safe During Pregnancy?

Zyflo® (zileuton) may not be safe for women who are pregnant. In previous animal studies involving Zyflo and pregnancy, the drug caused problems in the fetal animals.

Zyflo and Pregnancy Category C

The U.S. Food and Drug Administration (FDA) uses a pregnancy category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Pregnancy Category C is given to medicines that have not been studied in pregnant humans but do appear to cause harm to the fetus in animal studies. Also, medicines that have not been studied in any pregnant women or animals are automatically given a pregnancy Category C rating.
When given to pregnant rats at high doses, Zyflo increased the risk of low birth weight and skeletal birth defects. When given to pregnant rabbits, Zyflo caused birth defects, including cleft palate.
However, it is important to note that animals do not always respond to medicines in the same way that humans do. Therefore, a pregnancy Category C medicine may be given to a pregnant woman if her healthcare provider believes that its benefits to the pregnant woman outweigh any possible risks to her unborn child.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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