The trans-3;4-dichloro-N-(2-(dimethylamine) cyclohexyl) labelled as U-47700 has a high affinity with the selective receptor, considered to have 7.5 times the binding affinity of morphine; as a result, it is sold as a recreational drug because of its analgesic and euphoric effects. Several toxicity cases and some fatalities have been reported during 2016.

To describe the presence of trans-3;4-dichloro-N-(2-(dimethylamine) cyclohexyl) in samples delivered to Energy Control during 2016 in Barcelona.

From January 2016 to October 2016, 4031 samples were delivered and only those samples containing trans-3;4-dichloro-N-(2-(dimethylamine) cyclohexyl) were studied, 6 of them were analysed as U-47700 (0.148%). Samples were analysed by energy control, a Spanish harm-reduction NGO that offers users the possibility of analysing the substances they intend to consume. Analysis was done by gas chromatography–mass spectrometry.

From the 6 samples that were analysed as trans-3;4-dichloro-N-(2-(dimethylamine) cyclohexyl), the presentation of 4 of them was white powder and the rest were not described. The procedence of the samples was Canada (2), USA (1), Sweden (1), Holland (1) and the remaining sample was not described. All samples were received during 2016.

The use of trans-3;4-dichloro-N-(2-(dimethylamine)cyclohexyl) is progressively increasing in Barcelona. Its harmful effects are being reported in recent medical literature and consumption represents an emerging issue, gaining popularity among recreational opioid users. It is potentially lethal when mixed with depressants like alcohol or benzodiazepines and overdose risk is higher compared to other opioids. This drug is not being detected by routine in medical test.

The authors have not supplied their declaration of competing interest.