Absorption of DTPA from the respiratory tracts of Beagle dogs

Absorption of diethylenetriaminepentaacetic acid (DTPA) from the nasopharyngeal (NP), tracheobronchial (TB) and pulmonary (P) regions of Beagle dogs was determined because of the current interest in aerosolized DTPA as a method for removal of internally deposited radionuclides. Radiolabeled DTPA was instilled into the NP, TB and P regions of Beagle dogs and its subsequent translocation was followed for 48 hours. Results revealed that 16, 48 and 90% of the instilled DTPA was absorbed into the circulatory system from the NP, TB and P regions, respectively. A comparison was also made between NP absorption of aerosolized DTPA and DTPA instilled into the nasopharynx. Nasopharyngeal absorption of aerosolized DTPA, 23%, was slightly higher than that of instilled DTPA. Diethylenetriaminepentaacetic acid deposited in the respiratory tract remained in the body longer than intravenously injected DTPA. These findings indicate that substantial absorption of DTPA occurs from all regions of the respiratory tract and that DTPA need not be deposited deep within the respiratory tract to produce systemic absorption of DTPA for the removal of internally deposited radioactive isotopes