The U.S. Food and Drug Administration is investigating an ingredient in adult laxatives that are commonly prescribed for children. Polyethylene glycol 3350 (PEG 3350) is the active ingredient in Miralax and other similar products, which are not approved for long-term use even in adults—yet they are commonly prescribed long-term in children.

While only very small amounts of PEG 3350 are believed to be absorbed by the intestines, there are concerns that data in children are lacking, especially in very young or chronically constipated children. The FDA has received reports of tremors, tics, and obsessive-compulsive behaviors in children taking laxatives containing this ingredient. The FDA has asked a team of scientists to investigate whether PEG 3350 is absorbed by very young children and whether it is associated with psychiatric problems.

“Every pediatric GI physician, I would guarantee you, has told a family this product is safe,” stated Kent C. Williams, MD. Now, “it may not be true.”

Previously the FDA tested eight batches of Miralax and found tiny amounts of ethylene glycol (EG) and diethylene glycol (DEG)—ingredients also found in antifreeze—in each batch. Ethylene glycol produces the same psychiatric symptoms as have been reported as adverse events of Miralax consumption to the FDA. While these levels complied with international safety standards, according to the label many people, children included, are prescribed Miralax for more than the recommended seven days.

The new study will investigate whether these ingredients are absorbed by children who have been taking the laxative for at least a month. Meanwhile, steer clear of polyethylene glycol. There are many natural laxatives available as well as methods of addressing constipation without having to resort to this potentially toxic chemical.