Disposition of phencyclidine and its pyrolytic products in mice exposed to smoke

Phencyclidine (PCP) is a drug that is frequently misused by smoking. Recent popularity of PCP abuse by this method probably stems from the fact that smoking allows users to titrate themselves as well as reduce the incidence of adverse reactions. PCP is pyrolyzed at high temperatures to form predominantly 1-phenyl-1-cyclohexene (PC). Piperidine and related products are formed in smaller quantities. Smoke from cigarettes impregnated with PCP contains approximately equimolar concentrations of PCP and PC. It has been shown that PCP and PC are present in the circulation of individuals after they smoke PCP-laden cigarettes. In addition, PCP and PC can be found in plasma as well as in all major organs of mice exposed to smoke from PCP-containing cigarettes. The brain concentrations of PC in mice are comparable to those of PCP immediately after exposure but the PC levels decline somewhat more rapidly. Actually the time course of behavioral activity correlates better with PCP levels than with PC levels. In addition, PC and its major metabolites, as well as piperidine, are considerably less active behaviorally than PCP, which suggests that pyrolysis represents an inactivation process for PCP. However, a total lack of contribution of pyrolysis products to PCP's actions has not been ruled out.