How Does the Benzamide Antipsychotic Amisulpride get into the Brain?—An In Vitro Approach Comparing Amisulpride with Clozapine

This study evaluated the disposition of the two atypical antipsychotics, amisulpride (AMS) and clozapine (CLZ), and its main metabolite N-desmethylclozapine (DCLZ), to their target structures in the central nervous system by applying an in vitro blood–brain barrier and blood–cerebrospinal fluid (CSF) barrier based on monolayers of porcine brain microvessel endothelial cells (PMEC) or porcine choroid plexus epithelial cells (PCEC). Permeation studies through PMEC- and PCEC-monolayers were conducted for 60 min at drug concentrations of 1, 5, 10, and 30 μM applied to the donor compartment. PMEC were almost impermeable for AMS (permeation coefficient, P<1 × 10−7 cm/s) in the resorptive direction, whereas transport in the secretory direction was observed with a P (±SD) of 5.2±3.6 × 10−6 cm/s. The resorptive P of CLZ and DCLZ were 2.3±1.2 × 10−4 and 9.6±5.0 × 10−5 cm/s, respectively. For the permeation across PCEC in the resorptive direction, a P of 1.7±2.5 × 10−6 cm/s was found for AMS and a P of 1.6±0.9 × 10−4 and 2.3±1.3 × 10−5 cm/s was calculated for CLZ and DCLZ, respectively. Both, CLZ and DCLZ, could easily pass both barriers with about a five-fold higher permeation rate of CLZ at the PCEC. The permeation of AMS across the BBB was restricted partly due to an efflux transport. It is thus suggested that AMS reaches its target structures via transport across the blood–CSF barrier.