Aggregometric assessment of clonidine's impact on the efficacy of dual platelet inhibition.

Background: Clonidine is commonly used as a calmative and antihypertensive agent in perioperative care. Due to the drug's alpha-2-agonistic effects, it has recently been hypothesised that clonidine may affect platelet aggregability. The present investigation aimed to study the potential impact of clonidine on the efficacy of dual antiplatelet therapy.

Methods: In this prospective, observational, single-centre study, patients treated with dual antiplatelet therapy were screened for eligibility. The patients were enrolled in the study if ex vivo thrombin-induced (TRAPtest), arachidonic acid-induced (ASPItest) and adenosine diphosphate-induced (ADPtest) platelet aggregation, as measured using multiple electrode aggregometry (MEA; Multiplate, Roche AG, Grenzach, Germany), confirmed efficient dual platelet inhibition. Ex vivo induced platelet aggregation was assessed before (baseline) and 3 minutes after (T1) spiking blood samples with either 1 ng/mL clonidine or sodium chloride 0.9% (control group).

Results: In total, 34 patients were finally enrolled in the study. Compared with baseline, platelet aggregation in the ASPItest and ADPtest was significantly increased at T1 in both groups. Platelet aggregation in the TRAPtest remained unchanged between baseline and T1 in both groups. Comparing platelet aggregation at T1, we detected no differences between blood samples that were spiked with clonidine and blood samples that were spiked with sodium chloride 0.9% in the TRAPtest, the ASPItest, or the ADPtest.

Conclusions: The results of this study indicate that clonidine does not affect platelet aggregability in patients treated with dual antiplatelet therapy. The findings of the study also indicate that ex vivo induced platelet aggregation in the ASPItest and ADPtest increases with the duration between blood drawing and MEA analyses.