The disposition of fluphenazine was investigated in six healthy volunteers following oral administration (5 mg). Using a sensitive and specific GC-MS procedure plasma fluphenazine concentrations were measured up until 32 h after drug administration. Peak plasma concentrations varied widely (range: 0.26-1.06 ng/ml) and were observed at 2.8 +/- 0.5 h following fluphenazine administration. The apparent terminal elimination half-life of fluphenazine was 33.1 +/- 8.1 h. The area under the plasma concentration-time curve differed widely between subjects (range: 7.1-28.6 ng/ml h) suggesting large interindividual differences in the extent of fluphenazine presystemic elimination.