Tramadol and Its Influence on Platelet Function — An Ex Vivo Study

Tramadol, a weak μ-opioid receptor agonist and a widely used analgesic, also inhibits serotonin and norepinephrine reuptake, which could potentially influence platelet function. While the bleeding risk of selective serotonin reuptake inhibitors is well documented, the impact of tramadol on platelet aggregation, despite its widespread use, remains underexplored. Therefore, this study aims to elucidate tramadol's effect on platelet function. This single-center laboratory study involved healthy volunteers at the Medical University of Graz, Austria. Platelet function was assessed using light transmission aggregometry following the addition of tramadol in increasing concentrations (0, 500, 1500, 4500, and 9000 ng/mL) to blood samples. Baseline and post-tramadol-addition platelet aggregation was measured using adenosine diphosphate-induced (ADP), ristocetin-induced, and thrombin-receptor activating peptide-induced (TRAM) aggregation. Statistical analysis employed the Friedman test. Seven healthy volunteers could be included in the final analysis. Platelet aggregation was assessed after ex vivo addition of tramadol (500-9000 ng/mL). No significant differences in aggregation percentages were observed between tramadol concentrations and baseline inducing activation with ADP, ristocetin, or TRAP. These findings suggest that tramadol, at therapeutic and supratherapeutic concentrations, does not significantly impair platelet function in most individuals. This supports the general safety profile of tramadol regarding platelet aggregation.Tramadol appears safe concerning platelet function. Further research with larger cohorts is warranted to confirm these results and investigate potential interindividual variability in response to tramadol.