RESPIRATORY CLEARANCE OF AEROSOLIZED RADIOACTIVE SOLUTES OF VARYING MOLECULAR-WEIGHT

  • 1 May 1987
    • journal article
    • research article
    • Vol. 28  (5) , 894-902
Abstract
To determine the influence of varying molecular weight (mol wt) on respiratory clearance of aerosolized solutes, we studied eight radiopharmaceuticals, each administered to four dogs: sodium 99mTc pertechnetate (TcO4), 99mTc glucoheptonate ([99mTc]GH), 51Cr-ethylenedinitrotetraacetate ([51Cr]EDTA), 99mTc diethylenetriaminepentaacetate ([99mTc]DTPA), 111In diethylenetriaminepentaacetate ([111In]DTPA), 67Ga desferrioxamine mesylate ([67Ga]DFOM),99mTc dextran ([99mTc]DX) and 111In transferrin ([111In]TF). After aerosolization (0.8 m MMD, 2.4 GSD), clearance was determined for 30 min and then corrected by intravenous injection for nonairspace radioactivity. In-TF clearance (-0.11 .+-. 0.10 %/min) was lower than TcO4 (6.32 .+-. 0.62 %/min), [99mTc]GH (1.50 .+-. 0.37 %/min), [51Cr]EDTA (2.38 .+-. 1.02 %/min), [99mTc]DTPA (3.51 .+-. 0.40 %/min), [111In]DTPA (2.35 .+-. 0.42 %/min), [67Ga]DFOM (1.99 .+-. 0.49 %/min) and [99mTc]DX (1.81 .+-. 0.75 %/min) clearance (p < 0.001). TcO4 clearance was higher than others (p < 0.001). Technetium binding to DX was unsatisfactory; aerosolization caused unbinding from DTPA. We conclude that respiratory clearance of large mol wt solutes within 30 min is negligible and, that clearance of molecules between 347-5,099 daltons differs greatly, suggesting that binding and/or intrapulmonary retention affect transfer.