They're cheap, legal, popular, and readily available. Synthetic drugs are designed to create the same effects as marijuana, PCP, meth, heroin, etc. The media calls them 'designer drugs' because every time the DEA labels a chemical compound an illegal substance, the manufacturers in China replace it with another compound that is equally as harmful.
They are packaged with colorful cartoon icons, such as Scooby Doo to appeal to children. Sold via the internet or at numerous convenient stores, they are as easy to buy as chewing gum. Authorities have to prove that these drugs were sold with the intent to consume, which is difficult because they are falsely marketed as potpourri or labeled "not for human consumption."
The effects of synthetic drugs are unpredictable due to the ever-changing variety of substances used in the manufacturing process. Users have been known to suffer paranoia, cardiac arrest, seizures, permanent brain damage, and death. Not knowing what specific chemicals are in the drugs make it extremely difficult for the ER doctor to treat victims.