Tissue distribution and lung localization of [14C]azelastine in guinea pigs.

Tissue distribution was performed in male guinea pigs that received a single oral dose of 1 mg/kg [14C]azelastine. Determination of 14C concentrations by liquid scintillation counting in 16 tissues and by whole-body autoradiography showed preferential uptake of the radioactivity by the lung. The liver had a higher and all other tissues had lower concentrations of 14C than the lung. The lowest 14C concentrations were in the eyes and brain. Light microscopy autoradiography of lung and trachea sections indicated localization of 14C, possibly in alveolar macrophages. The radioactivity cleared completely from lung tissue, as well as from other tissues within 48 hr.