A trial of dipyridamole and aspirin in the prevention of smoking-induced changes in platelets and endothelium in men with coronary artery disease.

A random-order, double-blind crossover study compared the effects of placebo, dipyridamole and dipyridamole plus aspirin on smoking-induced changes in endothelium and platelets. Each of 12 male habitual smokers with coronary artery disease was given dipyridamole (75 mg) and aspirin (324 mg), dipyridamole (75 mg) and placebo for aspirin, or a placebo for each drug 3 times daily for 1 week before each of three 20-minute periods (separated by 2 weeks) of smoking 2 cigarettes after a 12-hour period of abstinence. During each period of smoking there were increases in the mean values of the plasma concentrations of beta-thromboglobulin, platelet factor 4 and nicotine, the endothelial cell count and the blood level of carboxyhemoglobin. In addition, the mean platelet aggregate ratio decreased during each period. After administration of placebos for both dipyridamole and aspirin, the respective mean values +/- standard deviations before and after smoking were 28 +/- 8 and 30 +/- 7 ng/ml (beta-thromboglobulin), 7.4 +/- 1.0 and 8.2 +/- 1.4 ng/ml (platelet factor 4), 3.7 +/- 0.6 and 15.7 +/- 3.5 ng/ml (nicotine), 4.2 +/- 1.4 and 5.4 +/- 1.7/counting chamber (endothelial cell count), 5.0 +/- 2.2 and 6.6 +/- 2.2% (carboxyhemoglobin) and 0.80 +/- 0.07 and 0.68 +/- 0.10 (platelet aggregate ratio). Each of the differences between the means before and after smoking was statistically significant (p less than or equal to 0.02). Neither dipyridamole alone nor in combination with aspiring significantly affected the mean smoking-induced change in any of these variables.(ABSTRACT TRUNCATED AT 250 WORDS)