Local intra-arterial drug delivery for prevention of restenosis: comparison of the efficiency of delivery of different radiopharmaceuticals through a porous catheter.

Rationale and Objectives: Several radiopharmaceuticals were administered through a porous balloon catheter to compare the absolute amount deposited and the retention in the vessel wall. The reported efficiency of local drug delivery ranges from 0.001% to 0.1%, with poor retention after 24 hours.
Methods: An endothelin derivative (n = 6), pertechnetate (n = 6), hexamethylpropylene amineoxime (HMPAO) (n = 5), ethyl cysteinate dimer (ECD) (n = 5), and tin colloid (n = 5) were labeled with 185 MBq/mL 99m-technetium. After balloon denudation of the infrarenal aorta in 27 New Zealand White rabbits, 100 microL of each agent was administered through a porous balloon at a pressure of 4 bar. Dynamic and static whole-body scintigrams were obtained for 24 hours. The infrarenal aorta was excised and the activity calculated in a gamma counter.
Results: Apart from their retention in the region of local administration, the radiopharmaceuticals showed different distribution patterns. The highest regional tracer retention was observed with HMPAO. After administration of HMPAO, a significant difference between regional (vessel wall plus surrounding tissue: 14.5% of injected dose [ID]/24 hours) and local (vessel wall: 1.8% ID/24 hours) delivery was found. In contrast, ECD was eliminated quickly (local retention after 24 hours = 0% ID). The retention efficiencies were HMPAO > endothelin derivative > tin colloid > pertechnetate > ECD.
Conclusions: The different physicochemical and pharmacokinetic properties of radiopharmaceuticals resulted in different delivery efficiencies after local application.