Plasma protein binding of perazine and amitriptyline in psychiatric patients

Summary The free fraction of amitriptyline (AT), measured by equilibrium dialysis in plasma from 29 AT-treated depressed patients, was 5.4–9.8% (mean 7.7%), which was the same as the values in 26 healthy controls (4.9–9.6%, mean 7.6%). The plasma levels of lipoproteins, as reflected by total cholesterol, and of ₁-acid glycoprotein (₁-AGP) did not differ between the two groups. The free fraction of AT in both exhibited a significant negative correlation with the concentrations of those two proteins. The unbound fraction of perazine (PER) was the same (3.1–5.9%, mean 4.4%) in plasma from 22 schizophrenic patients and from 24 healthy volunteers (2.9–6.0%, mean 4.5%). However, in patient plasma ₁-AGP was significantly higher (mean 1.07 vs 0.81 mg/ml) and total cholesterol tended to be lower (mean 173 vs 201 mg/100 ml) than in plasma from normals. In consequence, the free fraction of PER was negatively correlated with the ₁-AGP concentration in plasma from patients and with the cholesterol level in plasma from control subjects; the other correlations were not significant. In 7 patients, the ₁-AGP level was normal prior to PER treatment. Serial blood samples from 6 patients revealed a consistent elevation of ₁-AGP above its pretreatment level during 4 weeks of PER administration in 5 of the subjects and a transient increase in one other. While low lipoprotein levels in schizophrenics seem to be a disease-related trait, the increase of ₁-AGP may be a drug effect.