Use of technetium-99m HMPAO scintigraphy for the detection of amiodarone lung toxicity in a rabbit model

Amiodarone (AD) is a very effective anti-arrhythmic drug, but its use is of ten associated with serious pulmonary complications such as pneumonitis and interstitial pulmonary disease. The aim of this study was to investigate t he relationship between the amount of amiodarone intake land the related de velopment of lung toxicity) and the lung uptake of technetium-99m labelled D,L-hexamethylpropylene amine oxime (HMPAO). Eighteen white female New Zeal and rabbits were divided into three groups and fed AD by gavage at doses of 10 (group A), 50 (group B) or 150 (group C) mg/kg daily. Tc-99m-HMPAO scin tigraphy was performed at baseline and after 1, 2, 3 and 4 weeks of drug in take. Anterior images of 1 min duration were acquired at 30 min after the i njection of 37 MBq Tc-99m-HMPAO. Regions of interest (ROIs) were drawn on t he lungs (L) and the upper limb (B) as the background. L/B ratios were calc ulated using the mean counts. In groups A and B histopathological evaluatio n of the lungs of all rabbits was performed at the end of the 4 weeks of AD intake, while in group C it was performed at 2 weeks because of increased mortality. At baseline, mean L/B ratios for groups A, B and C were 2.8 +/-0 .3, 2.8 +/-0.3 and 2. 8 +/-0.4, respectively. After 3 weeks of AD intake, L /B ratios increased to 4.1 +/-0.6 and 4.8 +/-0.6 in groups A and B, respect ively. The L/B ratio was 3.6 +/-0.2 after 1 week of AD intake in group C. T he correlation coefficients between the lung uptake of Tc-99m-HMPAO and AD doses for groups A, B and C were r=0.51 (P=0.037), r=0.74 (P=0.0002) and r= 0.96 (P=0.0001), respectively. Histopathological findings related to AD lun g toxicity, such as interstitial pneumonitis and foamy alveolar macrophages , were observed more frequently in groups B and C than in group A. Accordin g to our findings, Tc-99m-HMPAO lung uptake is correlated with AD dose. Tc- 99m-HMPAO lung imaging can demonstrate AD-induced lung injury.