Development and validation of a precise flow injection method for the assessment of brexpiprazole, with application to pharmaceutical dosage forms and human plasma analysis

Abstract

A novel antipsychotic medication named brexpiprazole (BRX) is currently employed for the treatment of schizophrenia and other psychotic disorders. Because BRX’s molecular structure includes a benzothiophene ring, it natively fluoresces. To detect BRX with precision and speed, a flow injection-fluorometric method, which is both sensitive and selective, is recommended. The fluorescence detection was conducted at 364 nm following excitation at 326 nm to capture the strong intrinsic fluorescence of BRX. The carrier solution employed was a mixture of phosphate buffer (pH 4, 10 mM) and acetonitrile (50: 50, v/v), with a flow rate of 0.5 mL min^− 1. The calibration curve, based on peak areas, exhibited linearity within the concentration range of 20–350 ng mL^− 1, with a remarkable correlation coefficient (r²) of 0.9999. The limit of quantitation was 9.7 ng mL^− 1, and the limit of detection was found to be 3.2 ng mL^− 1. This method was applied to quantify BRX in Neopression^® tablets, achieving recovery within an acceptable range without interference from the tablet’s additives. Additionally, the proposed approach was successfully utilised to quantify the drug in spiked human plasma. The approach underwent validation following ICH requirements.