Lung clearance of inhaled 99Tcm-erythromycin lactobionate in non-smokers and smokers.

99Tcm-labelled erythromycin lactobionate (99Tcm-EL) was used as a radioaerosol for lung ventilation imaging in humans after animal studies had shown slow clearance of 99Tcm-EL from the alveolar spaces. We performed inhalation studies in 26 volunteers: 11 non-smokers, 13 smokers (3 of whom smoked one cigarette just before inhalation of 99Tcm-EL) and 2 patients with pulmonary emboli (PE). The PE patients were imaged by both 99Tcm-EL and xenon-133 (133Xe) for comparison. The image quality with 99Tcm-EL was comparable to that with 133Xe, showing good peripheral penetration. The biological clearance half-lifes for 99Tcm-EL were 3.9 +/- 1.1 h in the non-smokers, 5.9 +/- 2.2 h in the smokers and 9.8 +/- 6.6 h in the three subjects who smoked a cigarette just before inhalation of the aerosol. 99Tcm-EL was cleared more slowly in the smokers and after smoke exposure, which could have indicated alveolar macrophage uptake. 99Tcm-EL can be used as an alternative to 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA) in ventilation imaging, thus overcoming the problem of the fast clearance of 99Tcm-DTPA in smokers.