Four teens who overdosed on an herbal stimulant called "Green Hornet" were back home Monday after being rushed to the hospital Friday night in Colorado Springs, Colo.

According to the stepfather of one of the four boys, they took the legal stimulant and suffered seizures before being rushed to the hospital in what was described as "critical" condition.

“They were thrashing so much, the paramedics were afraid they might break some bones, so they had to strap them to boards,” Dan Hayes told the Colorado Springs Gazette

The directions on the bottle indicate a serving size is one ounce, 7NEWS reported.

Web sites selling the liquid said that effects from the stimulant last five hours.

Green Hornet is marketed as a dietary supplement, so it's not controlled by the Food and Drug Administration.

The store that sold the stimulant said it has a policy of not selling the liquid to anyone younger than 18. Two of the teens were 18 and two were 17.