SLC22A1 encodes organic cation transporter 1 (OCT1), a polyspecific membrane transporter that mediates facilitated transport of structurally diverse organic cations including drugs, toxins, and endogenous compounds 1. OCT1 is primarily localized to the basolateral membrane of hepatocytes, enterocytes, and renal proximal tubular cells, playing crucial roles in drug absorption, distribution, and elimination 1. The transporter exhibits classic Michaelis-Menten kinetics with a Km of approximately 14 μM for model substrates in primary human hepatocytes 2. OCT1 is clinically significant as a major determinant of metformin pharmacokinetics, the first-line diabetes medication 3. Genetic polymorphisms in SLC22A1, particularly rs628031, rs683369, and rs12208357, substantially affect drug transport activity and are associated with altered metformin plasma concentrations, therapeutic response, and HbA1c levels 34. These variants also influence response to other medications like imatinib in chr6 myeloid leukemia treatment 5. Additionally, certain SLC22A1 polymorphisms are associated with increased type 2 diabetes risk in Chinese populations 6. The transporter's broad substrate specificity and pharmacogenetic variability make it a critical factor in personalized medicine and drug-drug interactions 7.