Current Scheduling Status
Year(s) and type of review / ECDD meetings
Drug Class
ECDD Recommendation
Placed under surveillance
Recommendation (from TRS)
Substance identification
RCS-4 is chemically 4-methoxyphenyl(1-pentyl-1H-indol-3-yl)methanone.

Previous review
RCS-4 had not been previously pre-reviewed or critically reviewed by the Committee. A direct critical review was proposed based on information brought to WHO’s attention that RCS-4 is clandestinely manufactured, poses an especially serious risk to public health and society, and has no recognized therapeutic use by any party. Preliminary data collected from the literature and from different countries indicated that this substance may cause substantial harm and that it has no medical use.

Similarity to known substances and effects on the central nervous system
The affinity of RCS-4 for CB1 and CB2 receptors is not known, but RCS-4 is able to stimulate guanosine triphosphate (GTP) binding to rat brain cortical membranes in a specific CB1 receptor-mediated binding assay. Thus it is conceivable that its effects may show delta-9-THC-like features. While there were analytically confirmed cases of non-fatal intoxications, these also involved other confirmed synthetic cannabinoids. Detections of RCS-4 in instances of driving under the influence of the drug were also reported.

Dependence potential
There is some evidence to suggest that synthetic cannabinoid receptor agonists may be able to produce tolerance and withdrawal symptoms when substance use is abruptly discontinued following regular use of high doses. Further detailed studies on these properties of RCS-4 are warranted.

Actual abuse and/or evidence of likelihood of abuse
Survey data indicate that RCS-4, like a range of other synthetic cannabinoids, shows THC-like effects in humans. In a WHO survey, 19 Member States confirmed that there was recreational/harmful use of RCS-4.

Therapeutic usefulness
RCS-4 has no recorded therapeutic applications or medical use.

The Committee noted the challenges associated with the evidence base concerning the substance. Of particular significance was the lack of analytically confirmed cases of non-fatal and fatal intoxications involving RCS-4. The Committee recommended that RCS-4 not be placed under international control at this time but be kept under surveillance.