Quantification of Amlexanox in Beagle Dog Plasma by LC–MS/MS and Its Application in a Comparative Pharmacokinetic Study of Conventional and Sustained‐Release Tablets

ABSTRACT Amlexanox, a 5H‐benzopyranopyridine derivative with emerging therapeutic potential in metabolic and inflammatory diseases, lacks a validated analytical method for pharmacokinetic studies in beagle dogs. A sensitive LC–MS/MS method was developed and validated for amlexanox in beagle dog plasma according to ICH M10 guidelines. Propranolol served as internal standard. Samples were processed by protein precipitation, and separation was achieved on a CAPCELL PAK C18 column using gradient elution with water and acetonitrile (both containing 0.2% formic acid) at 400 μL/min. Detection used positive electrospray ionization with MRM of m/z 299.0 → 281.0 for amlexanox and m/z 260.0 → 116.1 for IS. The method showed good linearity over 40–2000 ng/mL ( R 2 > 0.99). All validation parameters met acceptance criteria. The method was applied to a three‐period fixed‐sequence study in beagle dogs ( n = 3, male) comparing intravenous injection (1 mg/kg), conventional tablets (75 mg), and sustained‐release tablets (150 mg). The sustained‐release formulation prolonged T max (3.67 vs. 1.00 h) and residence time (two‐fold increase in t 1/2 and MRT), and improved absolute bioavailability from 25.36% to 33.09% (relative bioavailability: 151.30%). These findings support the clinical development of a sustained‐release amlexanox formulation with reduced dosing frequency and improved patient compliance.