IMPROVED METHOD TO LABEL BETA-2 AGONISTS IN METERED-DOSE INHALERS WITH TC-99M

Labelling beta-2 agonists in a metered-dose inhaler (MDI) with technet ium-99m allows imaging of the depostition of the aerosol in the respir atory tract. We have developed an improved labeling method in which an hydrous pertechnetate is dissolved in a small volume of ethanol, dilut ed with a fluorocarbon, and introduced into a commercial MDI. Imaging the MDI demonstrated that the Tc-99m was associated with the active in gredient, not just the propellant. The method has been used successful ly with salbutamol and fenoterol MDIs and should be directly applicabl e to other MDIs which contain hydrophilic drugs.