The U.S. Food and Drug Administration (FDA) announced this week it is taking action to restrict illegal importing of the veterinary pharmaceutical xylazine, which has increasingly been found in illicit fentanyl and involved in a growing number of overdose deaths.

Xylazine is often mixed together with other substances including fentanyl. It is also being mixed with methamphetamine and cocaine.

The FDA’s action allows for shipments of xylazine and the ingredients used to make it to be detained, CBS News reports. Xylazine can cause serious and life-threatening effects in humans, including severe skin wounds and dead tissue, according to the FDA. It can depress breathing, blood pressure, heart rate and body temperature to critical levels.

“The FDA remains concerned about the increasing prevalence of xylazine mixed with illicit drugs, and this action is one part of broader efforts the agency is undertaking to address this issue,” FDA Commissioner Robert M. Califf, M.D., said in a news release.