Background: Clinical studies have suggested increased risk of thrombotic events after planned cessation of clopidogrel therapy, due to increased platelet reactivity (platelet rebound); however, in many studies platelet function was not assessed before introducing clopidogrel. Patients who are scheduled to stop clopidogrel therapy, do it abruptly, so a gradual drug cessation might provide a beneficial treatment strategy.

Aim: To determine whether a clopidogrel discontinuation results in platelet rebound hyperaggregability with increased activity compared to pre-treatment values and to assess whether abrupt or tapering clopidogrel cessation may affect platelet reactivity.

Methods: Patients with stable coronary artery disease (n = 49), on chronic acetylsalicylic acid treatment, who underwent coronary angiography, and were scheduled for elective percutaneous coronary intervention with stent implantation were en­rolled. Patients were randomised to either a tapering clopidogrel discontinuation during a two-week period (tapering group, n = 25) or abrupt drug cessation (abrupt group, n = 24). After 12 months of dual antiplatelet therapy with clopidogrel and acetylsalicylic acid, we performed three follow-up visits with blood sampling. Platelet aggregation was assessed using a mul­tiple electrode aggregometer at inclusion, at cessation day, and seven and 14 days after complete clopidogrel discontinuation. The primary endpoint was the level of adenosine-diphosphate (ADP)-induced platelet aggregation. We also analysed platelet function in the ASPI test and platelet count as secondary endpoints.

Results: In 36 patients included in the main analysis, we found significant differences between the two study groups in the levels of ADP-induced platelet aggregation at days seven and 14 after cessation of clopidogrel (p = 0.004 and p = 0.04, respectively). In the abrupt group, platelet aggregation returned to the values similar to baseline at day seven. There were no significant differences between baseline, seven, and 14 days after drug cessation (p = 0.92 and p = 0.37, respectively). However, in the tapering group, ADP values at seven and 14 days after drug cessation were significantly decreased, comparing to baseline (p < 0.0001 and p = 0.009, respectively). For the ASPI test and platelet count we did not find significant differ­ences between the groups. All values returned to levels similar to the baseline. During the follow-up there were no serious cardiovascular events or bleedings.

Conclusions: Tapering vs. abrupt discontinuation of clopidogrel treatment results in significantly lower platelet aggregation values after 14 days from complete drug cessation. We found no evidence of a platelet rebound effect.