Pharmacokinetic and Tissue Distribution Analysis of Scutellarin and Iso‐Scutellarin From Breviscapine Injection in Rats by a Validated UPLC‐MS/MS Method

ABSTRACT Breviscapine injection (BI), a standardized botanical drug for cardiovascular and cerebrovascular diseases, lacks adequate characterization of its pharmacokinetics and tissue distribution. A UPLC‐MS/MS method was developed and validated for simultaneous quantification of scutellarin and its metabolite iso‐scutellarin in rat plasma and tissues after intravenous BI administration. Sample preparation used methanol protein precipitation, with detection via positive electrospray ionization MRM. Validation followed the Chinese Pharmacopoeia and bioanalytical PK guidance. The assay showed LLQs of 10.0 ng/mL (scutellarin) and 5.0 ng/mL (iso‐scutellarin), good linearity ( r 2 ≥ 0.990), precision (RSD ≤ 11.1%), accuracy (91.7%–106.8%), and acceptable recovery and matrix effects. PK analysis revealed moderate‐to‐rapid systemic elimination of scutellarin. Both analytes distributed to tissues within 0.25 h postdose, with exposure ranking: bladder > small intestine > kidney > small intestine > kidney > stomach > liver > plasma > heart > skeletal muscle > pancreas > skin > fat > lung > ovary > testis > adrenal > heart > skeletal muscle > pancreas > thymus > spleen > brain. The method is suitable for BI studies. The limited brain penetration suggests formulation optimization to prolong plasma exposure may be worth exploring, and the relatively high hepatic distribution points to a potential need for monitoring liver and kidney function.