A designer drug is a structural or functional analog of a controlled substance that has been designed to mimic the pharmacological effects of the original drug, while avoiding classification as illegal and/or detection in standard drug tests. Designer drugs include psychoactive substances that have been designated by the European Union as new psychoactive substances (NPS) as well as analogs of performance-enhancing drugs such as designer steroids. Some of these were originally synthesized by academic or industrial researchers in an effort to discover more potent derivatives with fewer side effects and were later co-opted for illicit use. Other designer drugs were prepared for the first time in clandestine laboratories. Because the efficacy and safety of these substances has not been thoroughly evaluated in animal and human trials, the use of these drugs may result in unexpected side effects.