Variability of serum drug level following a single oral dose of dipyridamole.

Serum dipyridamole levels were measured in 27 patients undergoing planar thallium-201 myocardial perfusion scintigraphy after receiving a 300 mg oral dose. Mean serum dipyridamole level was 2.9 +/- 1.6 mcg/ml (range 0.2-5.7). No correlation was found between serum level and symptoms, heart rate or blood pressure response, peak heart to lung thallium activity ratio, peak heart to liver thallium activity ratio, or peak myocardial thallium washout. Serum level following a single oral dose of dipyridamole is unpredictable and patients with low drug levels cannot be easily identified at the time of study.