Absorption of diethylenetriaminepentaacetic acid (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 the removal of radionuclides deposited in the respiratory tract. Radiolabled DTPA was instilled into the NP, TB and P regions of 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 as opposed to instilled DTPA. Nasopharyngeal absorption (23%) of aerosolized DTPA was slightly higher than that of instilled DTPA. Further, DTPA deposited in the respiratory tract remained in the body longer than intravenously injected DTPA. These findings indicate that a substantial quantity of DTPA is absorbed from all regions of the respiratory tract and that DTPA need not be deposited within the deep lung to produce systemic absorption of DTPA for the removal of internally deposited radioactive isotopes.