Nasal Absorption of DTPA in Rats

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Abstract
Absorption of diethylenetriaminepentaacetic acid (DTPA) from the nasopharyngeal region of rats was determined because of the current interest in aerosolized DTPA as a method for the removal of radionuclides deposited in the respiratory tract. Radiolabeled DTPA aerosol particles with an activity median aerodynamic diameter (AMAD) of 8.7 micro m were inhaled by rats and their clearance was studied for 4 hr. Sixty-eight per cent of the deposited aerosol was absorbed into the general circulation but, when a correction was made for DTPA remaining in the nasal region at sacifice, the projected total absorption was 83%. In earlier studies, the direct absorption of a small amount of DTPA solution instilled into the nasal region was 19% but, when projected to total clearance of the chelate from the nasopharyngeal region, absorption was 30%. These findings demonstrate that nasal absorption of DTPA is an important pathway for the entry of DTPA into the blood. The possible use of a DTPA nasal mist for protracted chelation therapy in radioactive metal poisoning is discussed.