Drugs effect on platelet survival time: comparison of two pyrimido-pyrimidine derivatives in patients with aortic or mitral replacement.

A prospective randomized trial of the effects of 2 antiplatelet aggregating drugs, dipyridamole (375 mg/d), a related substance RA 233 (1500 mg/d) and placebo, concomitantly with oral anticoagulants, was carried out in patients with prior valvular replacement. The study was aimed to determine effect on platelet survival time (PST) of these 2 agents. The trial sample consisted of 40 males and 15 females aged 40-70 years (average 53 years). 32 received Björk-Shiley valve in aortic position, 23 underwent mitral valve replacement: 3 with Cooley-Cutter, 11 with Lillehei-Kaster 500 and 9 with Starr-Edwards 6120 prostheses; 28 patients had aortic stenosis, 21 aortic insufficiency. All the PST measured after 3 months of treatment were within normal ranges and not different between placebo, dipyridamole or RA 233 treated subjects: averages in days were, respectively, 7.49, 7.11 and 6.88. The present study did not support the claim that modern valve prosthesis could lead to a shortened PST.