An Associated Press analysis shows that the substances are increasingly causing users to fall seriously ill, with some suffering seizures and hallucinations.
Available in many head shops for as little as $10, some of the synthetic drugs are often packaged as incense or bath salts, but they don't perfume the air or soften water.
As more Americans experiment with them, the results are becoming evident at hospitals: a sharp spike in the number of users who show up with problems ranging from labored breathing and rapid heartbeats to extreme paranoia and delusions. The symptoms can persist for days.
At the request of the AP, the American Association of Poison Control Centers analyzed nationwide figures on calls related to synthetic drugs. The findings showed an alarming increase in the number of people seeking medical attention.
At least 2,700 people have fallen ill since January, compared with fewer than 3,200 cases in all of 2010. At that pace, medical emergencies related to synthetic drugs could go up nearly five times by the end of the year.
"Many of the users describe extreme paranoia," said Mark Ryan, director of the Louisiana Poison Center. "The recurring theme is monsters, demons, and aliens. A lot of them had suicidal thoughts."
The recent surge in activity has not gone unnoticed by law enforcement and elected officials.
The Drug Enforcement Administration recently used emergency powers to outlaw five chemicals in synthetic pot, putting them in the same category as heroin and cocaine.
But manufacturers are quick to adapt, often cranking out new formulas that are only a single molecule apart from the illegal ones.
On Wednesday, the Senate's Caucus on International Narcotics Control discussed curbing the growth of synthetics. "This is a whole new method of trafficking," testified Joseph T. Ranznazzisi, deputy assistant administrator in the DEA's office of diversion control. "We've never experienced this before, when the product is just on the shelf."
Sen. Charles E. Grassley (R., Iowa) introduced a measure bearing the younger Rozga's name that would permanently ban five chemicals in synthetic marijuana products.
Jan Rozga hopes the law will be her son's legacy. "I did not stop being David's mother when he died," she said. "I want to right that wrong for him."