Genetic Variation in CYP2D6 and SLC22A1 Affects Amlodipine Pharmacokinetics and Safety

Amlodipine is an antihypertensive drug with unknown pharmacogenetic biomarkers. This research is a candidate gene study that looked for associations between amlodipine pharmacokinetics and safety and pharmacogenes. Pharmacokinetic and safety data were taken from 160 volunteers from eight bioequivalence trials. In the exploratory step, 70 volunteers were genotyped for 44 polymorphisms in different pharmacogenes. CYP2D6 poor metabolizers (PMs) showed higher half-life (t_1/2) (univariate p-value (p_uv) = 0.039, multivariate p-value (p_mv) = 0.013, β = -5.31, R² = 0.176) compared to ultrarapid (UMs), normal (NMs) and intermediate metabolizers (IMs). SLC22A1 rs34059508 G/A genotype was associated with higher dose/weight-corrected area under the curve (AUC₇₂/DW) (p_uv = 0.025; p_mv = 0.026, β = 578.90, R² = 0.060) compared to the G/G genotype. In the confirmatory step, the cohort was increased to 160 volunteers, who were genotyped for CYP2D6, SLC22A1 and CYP3A4. In addition to the previous associations, CYP2D6 UMs showed a lower AUC₇₂/DW (p_uv = 0.046, p_mv = 0.049, β = -68.80, R² = 0.073) compared to NMs, IMs and PMs and the SLC22A1 rs34059508 G/A genotype was associated with thoracic pain (p_uv = 0.038) and dizziness (p_uv = 0.038, p_mv = 0.014, log OR = 10.975). To our knowledge, this is the first work to report a strong relationship between amlodipine and CYP2D6 and SLC22A1. Further research is needed to gather more evidence before its application in clinical practice.