The drug -- also called K2 and Spice -- is the third most abused drug by high school seniors in the state, behind actual marijuana and prescription drugs, the Philadelphia Inquirer reported.
Side effects of synthetic marijuana include seizures, dangerously elevated heart rates and hallucinations, the U.S. Drug Enforcement Administration reported.
"Today, we are ending this dangerous game played by drug dealers. We are making it unambiguously clear that if a synthetic chemical is being sold because it mimics the effects of marijuana, the dealer is committing a crime," Attorney General Jeffrey S. Chiesa said Wednesday.
Synthetic marijuana has been banned in 39 states, the newspaper reported.
Chris Goldstein, a board member of the Philadelphia chapter of the National Organization for the Reform of Marijuana Laws, called banning synthetic marijuana misguided, as politicians inevitably just bring more attention to the substance.
"The politicians end up being the biggest billboards selling this in their attempt to ban it," he said.