[New psychoactive substances in emergency medicine]

New psychoactive substances (NPS) are a heterogeneous group of synthetic intoxicating substances. What they have in common is their "new" appearance as a narcotic drug. Many of them imitate known drugs; some of them are derivatives of substances developed as drugs many years ago. Changed or completely newly developed chemical structures often give the NPS a massively increased effect. This includes not only the effects desired by the consumer, but also the undesirable effects with sometimes fatal consequences. The use of NPS has been an increasing phenomenon for years. In 2018, 2.6% of German adults had already had experience with NPS. NPS-intoxicated persons represent a challenge for the treating physicians not only because of the heterogeneity of the substances, but also because of the unpredictable effects for the users. The clinical assessment is often made more difficult due to the presence of a mixed intoxication. Only systemic toxicological analysis-generally not readily available-provides safety, as conventional rapid or bedside tests do not record many substances. There is no global definition of NPS. A practical, clinical classification differentiates into four groups: synthetic stimulants, synthetic cannabinoids, synthetic hallucinogens, and synthetic sedatives.