LUNG CLEARANCE OF INHALED TC-99(M)-ERYTHROMYCIN LACTOBIONATE IN NONSMOKERS AND SMOKERS

Tc-99(m)-labelled erythromycin lactobionate (Tc-99(m)-EL) was used as a radioaerosol for lung ventilation imaging in humans after animal stu dies had shown slow clearance of Tc-99(m)-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 Tc-9 9(m)-EL) and 2 patients with pulmonary emboli (PE). The PE patients we re imaged by both Tc-99(m)-EL and xenon-133 (Xe-133) for comparison. T he image quality with Tc-99(m)-EL was comparable to that with Xe-133, showing good peripheral penetration. The biological clearance half-lif es for Tc-99(m)-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. Tc-99(m)-EL was clear ed more slowly in the smokers and after smoke exposure, which could ha ve indicated alveolar macrophage uptake. Tc-99(m)-EL can be used as an alternative to Tc-99(m)-diethylenetriamine pentaacetate ((99)Tc(m)DTP A) in ventilation imaging, thus overcoming the problem of the fast cle arance of Tc-99(m)-DTPA in smokers.