Figure 1

Illustration of structural similarity. Using phencyclidine (PCP) as the target compound, 2D similarity was calculated using MDL public keys and the Tanimoto coefficient to five different compounds, three of which (dextromethorphan, meperidine, and the phencyclidine metabolite 4-phenyl-4-piperidino-cyclohexanol) have been reported to cross-react with at least some marketed PCP immunoassays, and two of which (ketamine and ibuprofen) have not been reported to cross-react with PCP screening assays. PCP has the highest similarity (in descending order) to 4-phenyl-4-piperidino-cyclohexanol, dextromethorphan, and meperidine. PCP has low structural similarity to ketamine (despite having similar pharmacological properties to PCP) and essentially no structural similarity to ibuprofen.