(CBS) — There’s a warning about a synthetic form of marijuana being sold on the streets of Chicago that was responsible for about two dozen visits to emergency rooms last week, reports WBBM’s Mike Krauser.

Illinois Poison Control Center Director, Dr. Carol DesLauriers says most of the 20 cases seen in Chicago emergency rooms last week involve a drug being sold as “Jamaican Party Spice.”

“Patients are coming into the hospital very confused,” she said. “They have very low blood pressure, low heart rate and some are even having seizures and kidney problems.”

DesLauriers says the long-term effects are as unknown as the ingredients.

“That’s kind of one of the problems,” she said. “You never really know what you are going to get. It could be a different substance from something that they’ve used in the past, it could be more potent, it could be contaminated.”

Synthetic marijuana and other drugs, once sold legally in some convenience stores as “K2” and “spice,” are illegal now.