ANTIAGGREGANT EFFECT AND TOLERABILITY OF CALCIUM CARBASALATE ADMINISTERED IMMEDIATELY AFTER AORTOCORONARY BYPASS - RESULTS OF A DOUBLE-BLIND PLACEBO-CONTROLLED STUDY

The patency of aorto-coronary bypasses is greatly influenced by platel et aggregability, and there is an associated risk of thrombosis which may occur very early during surgery, It is in this context that aspiri n has been the subject of successful clinical studies. When administer ing aspirin, it is preferable to choose formulations that are well tol erated by the gastro-intestinal tract. This was the reason for carryin g out the present randomised single-centre double-blind parallel-group study aimed at confirming the platelet anti-aggregant effect and tole rability of calcium carbasalate administered during the immediate post operative period. The dose prescribed was equivalent to aspirin 325 mg daily, and was given as a single dose 6 hours after the end of the op eration and repeated for 7 days, versus placebo, in 56 patients underg oing aorto-coronary bypass grafts. A clinical assessment, EGG, platele t count and measurements of CPK and CPK-MB were carried out daily for the 7 days of the study. Tests of platelet aggregation (to arachidonic acid, ADP and collagen), assays of serum thromboxane B-2, MDA and PDF , and urinary assays for beta-thromboglobulin and 6-keto-PGF-1 were ca rried out before treatment, then 1 and 7 days after the start of treat ment. Fifty males (89%) and 6 females, mean age 58.3 years, received t reatment with either calcium carbasalate (group C, n = 28) or placebo (group P, n = 28). The atheromatous lesions present in most cases repr esented triple-vessel disease (37 cases), and most operations were tri ple bypasses (23 cases) or double bypasses (20 cases). A significant r eduction in platelet aggregation to arachidonic acid and collagen on D 1 (p = 0.04) and D7 (p < 0.001), and to ADP on D7 (p < 0.01) was obser ved in group C as compared with group P. Group C also showed significa nt reductions as compared with group P in respect of serum thromboxane B-2 levels on D1 (p < 0.01) and D7 (p < 0.001) and MDP; levels on D1 and D7 (p < 0.001). No significant difference was demonstrated between the two groups in respect of urinary 6-keto-PFG-1 excretion. The numb er of patients showing a rise in CPK was lower in group C but this dif ference did not reach statistical significance. ST segments change wer e comparable in the two groups, and no patient complained of anginal p ain during the study. These results show that calcium carbasalate admi nistered at a dose equivalent to 325 mg aspirin daily caused very earl y inhibition of platelet aggregation, specifically inhibiting platelet production of thromboxane B-2 without altering prostacyclin levels. I n addition, calcium carbasalate was found to be well tolerated. This s tudy confirms the value of early administration of aspirin at a dose o f 325 mg daily during the hours immediately following aortocoronary by pass graft surgery.