CITRIC-ACID ENHANCES THE ANTITHROMBOTIC EFFECT OF ASPIRIN IN MANY ASPIRIN-RESISTANT SUBJECTS

This study had three objectives: (1) to determine the frequency of hig h platelet aggregators in a consecutive series of 268 apparently healt hy volunteers who presented to our Center; (2) to assess the inhibitor y effect of aspirin (ASA) on these high aggregators; (3) to determine, in a double-blind trial, whether or not the addition of citric acid ( CTA) to ASA would increase its inhibitory effect in subjects who had a suboptimal response to aspirin alone. A platelet aggregation-scoring methodology developed for turbidimetric platelet aggregometry was used to quantify baseline aggregation and medicinal effects. We define a h igh aggregator as one whose unmedicated PA score is greater than or eq ual to 30. We define the response of a high aggregator to ASA as poor if the medicated PA score stays at greater than or equal to 30. We fou nd that 58 of 268 apparently healthy unmedicated volunteers (22%) had PA scores greater than or equal to 30, and that 27 of these (47%) had a poor response to 325 mg ASA, with an average drop in their PA scores from 49.5 +/- 13.1 to 41.1 +/- 8.6 (16%). Twenty-five of these 27 peo ple were enrolled in the double-blind study comparing the effect of AS A and ASA + CTA on platelet aggregability. Of these high aggregators w ho had a poor response to ASA, 12 of 25 (50%) had a good response to 1 62.5 mg of ASA plus 162.5 mg of CTA, with an average drop of their PA scores from 46.7 +/- 13.2 to 22.0 +/- 5.2 (53%). CTA alone had no effe ct on the PA score, which was similar to the control placebo. Our data suggest that a 1:1 combination of ASA and CTA may offer significantly greater protection against arterial thrombotic events than ASA alone in subjects who respond poorly to ASA.