Unbound plasma concentrations, total plasma concentrations, and red blood cell concentrations of thioridazine and its main metabolites: an in vitro study.

The relationships between, on the one hand, the unbound plasma concentrations of thioridazine and thioridazine metabolites and, on the other, the total plasma concentrations and the red blood cell concentrations were studied in vitro. The relationships between the unbound and total plasma concentrations were curvilinear, while those between the unbound concentrations and the red blood cell concentrations within a broad range were closer to rectilinear. Profound changes were seen in the relationship between unbound and total plasma concentrations at varying concentrations of alpha 1-acid glycoprotein, while the rectilinear relationship between the unbound plasma concentrations and the red blood cell concentrations remained essentially unchanged.