A validated method for the determination of doxofylline and its pharmacokinetic application in healthy volunteers.

Background: Current HPLC-based methods for doxofylline analysis lack speed and precision. A rapid, specific, and sensitive UPLC-MS/MS method was developed for the determination of doxofylline in this study.

Research design and methods: This method was fully validated and doxophylline-d4 was used as an internal standard. A Kinetex-C18 column (EVO 100Å, 50 × 2.1 mm, 5 μm) was used for the separation procedure, with mobile phases consisting of 0.3% formic acid (A) and 90% acetonitrile solution with 0.3% formic acid (B). The total runtime of the gradient elution procedure was 2.6 minutes. The mass spectrometry analysis was carried out employing a multiple reaction monitoring model and using the transitions of m/z 267.000→181.000 for doxofylline and m/z 271.200→181.100 for the internal standard.

Results: The linear range of detection for doxophylline was between 20.0 to 16,000 ng/mL. The intra-batch accuracy deviations of each concentration level ranged from -8.0% to 2.5%, while the intra-batch precisions ranged from 1.3% to 9.0%. And the inter-batch accuracy deviations were -5.8% ~0.8%, while the inter-batch precisions were 2.2% ~7.0%.

Conclusions: This method was applied to pharmacokinetic clinical trials of single oral administration of doxophylline tablets successfully.

Clinical trial registration: www.clinicaltrials.gov identifier is CTR20240006 and CTR20233665.