Why are such small doses of dipyridamole used for stress testing but comparatively large doses used in tablets for post stroke? surely the 'stress test' like symptoms / side effects would be unbearable with 100mg x 3 a day? thank you?

Dipyridamole (persantine) is used to open the coronary arteries during the stress test with nuclear medicine. The diseased coronary vessel does not respond well with dipyridamole so that involved area will be identified by scan. The dose is small but it is given intravenously as a bolus so the effect is quite strong but not long lasting compared with the oral doses taken for people with stroke.