A burst of synthetic drug overdoses in downtown St. Louis is putting major pressure on local emergency rooms.

This week, first responders have taken dozens of calls for overdoses.

As of Saturday, the city of St. Louis reports a total of 135 overdoses since last Monday.

Most of the patients are homeless, and many are using K2, a type of synthetic marijuana. Firefighters and EMS report many of the victims are living at or near the New Life Evangelistic Center.

Doctors at St. Louis University Hospital started seeing a spike in synthetic drug overdose patients within the last week.

“We'll get anywhere between three and seven patients pretty darn quickly,” said SLU Care’s Dr. Laurie Byrne, the Chief of Emergency Medicine at SLU Hospital. “And we've been getting them throughout the day.”

Dr. Byrne estimates her ED has seen about 40 patients this week suffering from an overdose, most of them the result of synthetic drugs.

“The challenge with some of these patients is, they can be here for an hour or they can be here for 10 hours,” she said. “Sometimes they come in very violent. And they're not only a danger to themselves, but they’re a danger to my staff.”

Another challenge, said Dr. Byrne, is how long overdose patients need care. While some are stabilized quickly, others can take hours to manage -- and fill beds and require resources that could be used for other patients.

She says synthetic drugs are very dangerous, and often mistaken for traditional marijuana.

“You don’t know what you’re getting,” she said. “Don’t do it – it’s just not worth it.”