From:  AI-integrated nanotherapeutics for schizophrenia: advancing precision oral drug delivery

 Comparative pharmacokinetic limitations of representative oral antipsychotic drugs.

DrugSolubility/BCS profileFirst-pass metabolismMajor CYP metabolic pathwayApproximate oral bioavailabilityP-gp substrate characteristicsFormulation relevance
RisperidonePoor aqueous solubility; commonly classified as BCS class IIModerate hepatic first-pass metabolismMainly CYP2D6; minor contribution from CYP3A4Approximately 70%Risperidone and 9-hydroxyrisperidone interact with P-gp, which may limit brain exposureSolubility enhancement, controlled release, and transporter-aware brain delivery may improve consistency of exposure
OlanzapinePoor aqueous solubility; BCS class II drug with high permeabilityExtensive hepatic metabolism and first-pass effectMainly CYP1A2; minor CYP2D6 contribution; glucuronidation also involvedApproximately 60%Evidence suggests P-gp can limit brain penetration of olanzapineLipid-based and solubility-enhancing systems may improve dissolution and reduce exposure variability
QuetiapineLow aqueous solubility at intestinal pH; BCS class II behaviorExtensive hepatic first-pass metabolismMainly CYP3A4Approximately 9%Reported as a P-gp substrate; transporter involvement may influence CNS dispositionOral bioavailability enhancement, lymphatic transport, and sustained-release systems are particularly relevant
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BCS: Biopharmaceutics Classification System; CNS: central nervous system; CYP: cytochrome P450; P-gp: P-glycoprotein.