In March checkit! identified a particularly harmful composition in a sample passed off as heroin. In addition to the expected ingredients, the sample contained caffeine and the highly potent synthetic opioid fentanyl.

Fentanyl is a synthetic opioid and about one hundred times more potent than morphine. Fentanyl has already been associated with numerous life-threatening overdoses, which have also led to deaths as a result of respiratory depression. Mixed use with other centrally depressant substances is strongly discouraged. Furthermore, serious interactions with a number of medications are known.

Reports of synthetic opioids are increasing across Europe. Over the course of the last year, checkit! synthetic opioids were occasionally detected in various samples. Among other things, a sample labelled as a synthetic hallucinogen, which was purchased on the darknet, contained the synthetic opioid methoxyacetylfentanyl as an admixture.

The term "synthetic opioids" refers to substances that are produced synthetically and have a similar effect to natural opiates (e.g. morphine) or heroin. The potency of these substances is often many times higher than that of morphine, which makes dosing difficult or even impossible without a laboratory balance (e.g. carfentanyl is already effective in the lower microgram range). Even careless handling of some substances can be life-threatening.