This work aimed to deepen the lately acquired knowledge about parenteral nanoemulsions as carriers for brain delivery of risperidone, a poorly water-soluble antipsychotic drug, through establishing the prospective relationship between their physicochemical, pharmacokinetic, biodistribution, and behavioral performances. For this purpose, two optimized risperidone-loaded nanoemulsions, stabilized by lecithin or lecithin/polysorbate 80 mixture, and costabilized by sodium oleate, were produced by high-pressure homogenization. The characterization revealed the favorable droplet size, narrow size distribution, high surface charge, with proven stability to autoclaving and long-term stability for at least one year at 25±2°C. Pharmacokinetic and tissue distribution results demonstrated improved plasma, liver, and brain pharmacokinetic parameters, resulting in 1.2-1.5-fold increased relative bioavailability, 1.1-1.8-fold decreased liver distribution, and about 1.3-fold improved brain uptake of risperidone active moiety following intraperitoneal administration of nanoemulsions relative to solution in rats. In behavioral study, investigated nanoemulsions showed pronounced reduction in basal and, more pertinently, amphetamine-induced locomotor activity in rats, with an early onset of antipsychotic action, and this effect lasted at least 90min after drug injection. Together, these findings corroborate the applicability of parenteral nanoemulsions as carriers for enhanced brain delivery of risperidone, further suggesting their promise in acute psychosis treatment or other emergency situations.
Keywords: Antipsychotic efficiency; Long-term stability; Parenteral nanoemulsion; Pharmacokinetics; Poorly water-soluble drug; Tissue distribution.
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