The agency says there have been several reports of severe health risks, including irregular heartbeats, cardiac arrest, and sudden death, associated with use of the drug that have led to its withdrawal from the market in several countries.
Researchers say domperidone is also excreted in breast milk and may expose infants to unknown health risks.
FDA officials say they issued the warning after they discovered that some women who breastfeed and/or pump breast milk are purchasing domperidone from compounding pharmacies and from foreign countries to increase their breast milk production.
Domperidone has not been approved for use in the U.S., and officials say use of the drug for any purpose is illegal.
Domperidone may increase the secretion of the hormone prolactin, which is needed for lactation. However, due to the risk of serious adverse effects, the FDA recommends that breastfeeding women not use the drug to increase milk production.
Warnings Issued on Domperidone
In addition to advising women not to use the drug, this week the FDA also issued six letters to pharmacies that compound drug products containing domperidone and firms that distribute them.
The letters state that that all drug products containing domperidone are illegal and selling or distributing them violates U.S. law.
Officials say domperidone is approved for use in several countries outside the U.S. to treat some stomach disorders. But it is not approved in any country for enhancing milk production.