The Drug Enforcement Administration is carrying out their biggest sweep against designer synthetic drugs this week.

Law enforcement officers carried out more than 150 arrest warrants and nearly 375 search warrants in 35 U.S. states and five countries Wednesday, the DEA said. More than 770 pounds of synthetic drugs have been seized in the last three days, said MSNBC.

DEA officials told a news conference that colorfully packaged drugs with such names as "Rush," "Spice" and "Mister Happy" were being targeted at teenagers and young adults through stores and street sales. 

Designer synthetic drugs are often marketed as herbal incense, bath salts, jewelry cleaner or plant food. They are made up of plant material that has been infused with psychoactive compounds that mimic THC, the active ingredient of marijuana, the DEA said. 

Abuse of the drugs can lead to seizures, vomiting, loss of consciousness and overdose deaths, the DEA said in a statement. The number of emergency room visits associated with the drugs reached 28,531 in 2011, more than twice the number the year before, it said. 

Since the agency's campaign against designer synthetic drugs began in December 2012, more than 75 arrests have been made and nearly $15 million in cash and assets seized, it said.