Abstract
To establish an in vivo method to determine nasal drug absorption and clearance from the nasal cavity, a rabbit's esophagus was cannulated with a tube, and a fluorescein/microcrystalline cellulose powder formulation was administered intranasally after recovery from anesthesia. The volumes of secreted mucus were constant during the experiment and not significantly different from those of non-administered rabbits. Fluorescein in the mucus showed a first-order clearance from the cavity. Plasma fluorescein concentration profiles of the operated group were similar to those of the control (non-operated) group. The total amount of fluorescein eliminated into the esophagus, remaining in the cavity, and absorbed from the cavity corresponded to almost 90% of the administered dose. This method allowed simultaneous determination of fluorescein absorption and clearance from the nasal cavity, which may be useful in any quantitative pharmacokinetic analysis of nasal drug delivery.
