New synthetic opioids (NSOs) and other new psychoactive substances (NPS) are increasingly present on the recreational drug market. In the context of the Synthetic Opioids Comprehensive Response Toolkit for European Stakeholders project, this tender describes a comprehensive approach for the pharmacological characterization of emerging NSOs and other NPS using in vitro and in vivo methods. To this end, the tender is proposed by a consortium of four independent academic laboratories. Importantly, all laboratories have demonstrated expertise in the pharmacological characterization of NPS, and existing collaborations are readily in place – as evidenced by peer-reviewed publications.