In vivo systemic evaluation of nasal drug absorption from powder formulations in rats.

Despite the potential benefits of nasal drug delivery, there is a need for a systematic evaluation of the efficacy of powder formulations adhering to the nasal mucosa. This study aims to establish a systematic evaluation method for nasal drug absorption from powder formulations. We selected three model compounds-antipyrine, griseofulvin, and acyclovir-and analyzed their pharmacokinetics following nasal administration of powder formulations under physiological conditions. Our experimental design incorporated assessments of the drug absorption patterns. Antipyrine demonstrated rapid absorption exclusively from the nasal cavity. In contrast, griseofulvin exhibited absorption from the nasal cavity and the gastrointestinal tract. This phenomenon could be attributed to the rapid nasal clearance of the drug with an initial half-life of 5 min. To further establish the physiological validity of our method, we conducted an experiment to investigate the impact of changing the mucociliary clearance (MC) on nasal absorption that resulted in a 1.2-fold increase in the bioavailability of acyclovir upon prolonged MC. Our findings support the utility of established methods in evaluating nasal absorption and their behavior in the nasal cavity. This study holds a promising advancement toward effective drug delivery via nasal administration, potentially leading to targeted delivery and improved therapeutic outcomes.