Synthetic mimics of marijuana, dissociative drugs and stimulants — such as the “bath salts” allegedly consumed by Randy Eugene, the Florida man shot after a horrific face-eating assault — are growing in popularity and hard to control. Every time a compound is banned, overseas chemists synthesize a new version tweaked just enough to evade a law’s letter.

It’s a giant game of chemical Whack-a-Mole.

“Manufacturers turn these things around so quickly. One week you’ll have a product with compound X, the next week it’s compound Y,” said forensic toxicologist Kevin Shanks of AIT Laboratories, an Indiana-based chemical testing company.

 “It’s fascinating how fast it can occur, and it’s fascinating to see the minute changes in chemical structure they’ll come up with. It’s similar, but it’s different,” Shanks continued.