Platelet survival was prolonged in rabbits which had been on sulfinpyrazone for 30 days or more. This was not accompanied by changes in tests of blood coagulation in vitro. Thrombus formation in flowing blood was on the average less, but not significantly so.
The mechanism of the change in platelet economy is unknown. It does not appear to depend on blood coagulation and cannot be explained by serum uric acid which does not occur in the rabbit. It may be attributable to changes in the platelet membrane which may also account for the increase in serotonin uptake.