Comparison of two and three compartment models of phencyclidine in man

A pharmacokinetic analysis comparing a 2 and 3 compartment model was performed on the published data of Wall et al. (12) on the kinetics of phencyclidine (PCP). These investigators gave 100 micrograms (mean 1.3 micrograms/kg) of 3H-PCP i.v. to three human volunteers and followed the plasma disappearance of PCP over 72 hr. They suggested that PCP followed a 2 compartment model with a plasma half life of 7-16 hr. In the present analysis, additional pharmacokinetic estimations from the plasma data were made and a 3 compartment model developed. The results obtained suggest complex PCP kinetics involving an initial pi half life of 5.5 min, an alpha half life of 4.6 hr, and a beta half life of 22 hr. The volume of distribution was large, varying from 2.2 to 2.4 1/kg for each compartment, suggesting binding of PCP.