Drug Distribution Studies

Two studies were carried out to evaluate drug distribution in the gut and in the lung. Producing a true tracer situation is important to these studies. In the analysis of modified-release formulations, drugs such as dilti-azem are formulated with small amounts of stable [152Sm]-samarium oxide. The tablets can then be activated by neutron activation to produce radioactive 153Sm and followed in vivo using planar imaging. This Phase I study allowed quantitative distribution of the tablet in the gastrointestinal tract [7]. In another example, the lung distribution of the corticosteroid tri-amcinolone acetonide was studied using the dispenser Azmacort, a pressurized aerosol metered-dose inhaler formulation. The steroid was radiolabelled with 11C and introduced into the dispenser. The time-activity curve obtained using PET showed a significant increase of the steroid in the lung and a significant decrease in the mouth (Fig. 17.3). These data were submitted to the FDA in support of the Azmacort inhaler's superiority [8].

Figure 17.3. Azmacort distribution in airway, lung, GI tract after administration. 3-D translucent, low-resolution CT (flesh tone) overlaid with the PET image of drug concentration (green).

Was this article helpful?

0 0

Post a comment