Better increase in fibrin gel porosity by low dose than intermediate dose acetylsalicylic acid

Aim To investigate the influence on plasma fibrin gel structure of low and intermediate doses of acetylsalicylic acid in healthy individuals. The influence of acetylsalicylic acid on thrombin formation, fibrinolytic capacity and plasminogen inhibitor-1 in plasma was also investigated. Methods Nineteen subjects were treated with 75 mg and 11 with 320 mg acetylsalicylic acid daily; eight subjects received both doses. Fibrin gel structure was determined by a permeability technique yielding a porosity constant (K-s), and the thromboxane metabolite 11-dehydro-thromboxane B-2 (TxM) was determined by an ELISA. Results Acetylsalicylic acid increased fibrin porosity by 65% at 75 mg (P<0.001, n=19), whereas lower increases were found at 320 mg (+22%, P<0.05, n=11). One week after withdrawal K-s had essentially returned to baseline (ns). Urinary thromboxane metabolites were suppressed during treatment (-61%, P<0.001 at 75 mg, n=19; -46%, P<0.01 at 320 mg, n=11). The intra-individual comparison showed similar results (K-s+92%, TxM - 62% at 75 mg; K-s+5%, TxM-52% at 320 mg). Fibrinolytic capacity, plasminogen inhibitor-1 levels and thrombin generation tin platelet-poor citrated plasma) were not influenced. Conclusion Low dose acetylsalicylic acid causes the greatest increase in fibrin gel porosity; this may well be of therapeutic importance.