Comparison of Anti-Platelet Efficacy of Four Different Marketed Formulations of Aspirin in Diabetic Patients

In India, Aspirin is marketed as multiple preparations for antiplatelet use and its drug release pattern is likely to affect efficacy. Objectives: The study compares anti-platelet efficacy of four preparations of aspirin against ADP-induced platelet aggregability and bleeding time (BT); and assesses correlation between steady state plasma concentration (CSS) and antiplatelet effect of daily 150mg Aspirin. Methods: This was a four armed, randomised, investigator-blinded, parallel-group, comparative study. Study was conducted in 121 subjects of Type 2 DM on oral anti-diabetics having one or more cardiovascular risk factors. Each subject was randomized to receive Plain aspirin, soluble, effervescent or enteric coated, for 15 days. Blood samples were taken at day 0 and day 15, two hours after dosing. Results: Total 121 subjects completed study (Plain 30, soluble 31, effervescent 30 and enteric coated 30) and the baseline characteristics were similar among all groups. All preparations inhibited platelet aggregation (Reduction from day 0 to day 15: plain-25.9%, soluble-23.9%, effervescent-23.5%, enteric coated-26.4%; p=0.89) and increased BT (Rise: plain-236.4%, soluble-236.1%, effervescent-229%, enteric coated-256.7%; p=0.87) to a similar extent. Salicylate CSS measured at day 15 was significantly higher in effervescent (23.75mg/L) as compared to enteric coated (19.73mg/L) and soluble (19.27mg/L). Plain aspirin produced salicylate CSS of 20.8mg/L. There was no significant correlation between salicylate CSS and antiplatelet activity for study population [r= -0.124, p= 0.179] or for individual groups. Conclusions: -All preparations produced comparable antiplatelet effect which did not correlate with steady state plasma salicylate concentration at daily dose of 150mg.