Illinois officials are warning of a spike in the number of patients going to emergency rooms after using dangerous synthetic drugs.

The Illinois Poison Center on Tuesday said it has received almost 20 calls from emergency departments about the drugs in the past week. According to the center, that's an increase of 600 percent compared with the typical week.

Synthetic cannabinoids are sometimes sold under names such as "K2" and "spice."

Dr. Michael Wahl is the center's medical director. He says emergency departments are reporting patients with severe symptoms such as seizures and coma. Most of those cases involved drugs sold in Chicago as "Jamaican Party Spice."

The drugs also can cause confusion, agitation, vomiting, psychosis and heart palpitations.

Wahl calls the increase "troubling."

Spencer Platt, Getty Images