Role of CYP2D6 polymorphisms in tramadol metabolism in a context of co-medications and overweight

Very few quantitative data exist on tramadol metabolites, which hampers our understanding of their role in efficacy and safety of tramadol. We aimed to provide quantitative data on tramadol and its 5 main metabolites in a patient cohort and to determine whether metabolite ratios can be predictive of a CYP2D6 metabolism phenotype. We also aimed to investigate the influence of co-medications and patient profile (BMI, glycemia, lipid levels) on tramadol metabolite ratios. Overall, 37 patient samples from the CONSTANCES cohort contained tramadol and its 5 metabolites. Mean concentrations found tramadol at 343.2 ± 223.2 μg/L, M1 at 62.4 ± 41.4 μg/L, M2 at 210.0 ± 272.3, M3 at 1.76 ± 3.0 μg/L, M4 at 1.8 ± 2.8 μg/L and M5 at 31.8 ± 28.4 μg/L. The most frequent CYP2D6 phenotype was extensive metabolizers (51.3%), followed by intermediate metabolizers (24.3%) and poor metabolizers (10.8%). CYP2D6-inhibiting co-medications impacted tramadol metabolism independently of CYP2D6 metabolism phenotype. Lipid parameters and glycemia were significantly associated with changes in tramadol metabolic ratios. Metabolic ratios are not sufficient to determine the CYP2D6 metabolic phenotype in patients. CYP2D6 inhibitors and obesity/NAFLD/diabetes impact tramadol metabolism. These factors are likely to impact the analgesic efficacy and safety profile of tramadol, justifying the need for further studies in this area.