Phencyclidine and phenylcyclohexene disposition after smoking phencyclidine.

Five men who smoked parsley cigarettes containing 100 micrograms of [3H]-phencyclidine hydrochloride (PCP.HCl) inhaled 69 +/- 5(SEM) % of the total radioactivity in the cigarette. Both PCP and its pyrolysis product, 1-phenylcyclohexene (PC), were found and measured in plasma. Calculations based on the assumption that the ratio of these two products was the same as in simulated smoking studies and based on either area under the curve or urinary excretion of PCP indicated that most of the PCP in smoke was absorbed. Mean half-life (t1/2) of PCP (24 +/- 7 hr, harmonic mean 18 hr) and ratios of metabolites in plasma and urine were close to those previously reported after intravenous and oral doses. A second peak in PCP plasma concentrations was observed, possible due to show efflux from the lungs. PC plasma concentrations (maximum 0.35 +/- 0.06 pmol/ml) were lower than those of PCP (maximum 0.62 +/- 0.09 pmol/ml) and its mean t1/2 (14 +/- 3 hr, harmonic mean 12 h) was shorter than that of PCP. Only traces of PC were found in urine. Only small amounts of metabolites from PC were found nonconjugated in plasma (to about 0.1 pmol/ml) or urine (less than 2% of radioactivity), but larger quantities were found as enzyme-hydrolyzable conjugates in urine (6% of radioactivity). Conjugates were also found in plasma (to about 0.12 pmol/ml).