Inhibition of platelet release reaction by acetylsalicylic acid.

The inhibitory potency and duration of action of single doses of aspirin B.P., claradin (a low sodium effervescent preparation of acetylsalicylic acid) and aloxiprin (an aluminium co-polymer of acetylsalicylic acid) on platelet release reaction induced by adenosine diphosphate (ADP) were studied in seventeen volunteers. Aspirin B.P. and claradin at 300 mg and 150 mg inhibited release reaction in all subjects within 24 hr; 75 mg was effective only in some subjects. Aloxiprin gave less marked response and a dose of 300 mg was required to inhibit the effect in all volunteers. Where occurring, inhibition of release reaction persisted for three days after treatment with all preparations and restoration to normal occurred in most subjects by the sixth day. A daily dose of 50 mg claradin for 12-15 days in five volunteers produced complete inhibition of release reaction for most of the treatment period. Inhibition of release reaction took up to 3 days to occur. Normal aggregation returned within 3 days of discontinuing treatment in all subjects. A daily dose of 25 mg claradin gave inconsistent results. It is suggested that if a trial of acetylsalicylic acid be undertaken for the prevention of arterial thrombosis based on its ability to inhibit platelet release reaction then a daily dose of 50 mg would be sufficient.