SLCO1B1 encodes organic anion transporting polypeptide 1B1 (OATP1B1), a sodium-independent transporter that mediates hepatic uptake of diverse endogenous and exogenous substrates. The transporter has broad substrate specificity, accepting bile acids, conjugated steroids, eicosanoids, and thyroid hormones. SLCO1B1 plays a critical role in hepatic clearance of bilirubin glucuronides and coproporphyrins, contributing to detoxification pathways. Functionally, the transporter uses bicarbonate as a probable counteranion and exhibits pH-sensitive substrate specificity, with enhanced transport in acidic microenvironments. Clinically, SLCO1B1 is essential for statin pharmacokinetics. The gene mediates hepatic uptake of all major statins—simvastatin, pravastatin, pitavastatin, atorvastatin, rosuvastatin, fluvastatin, and lovastatin—and thereby regulates systemic drug exposure 1. Genetic variants in SLCO1B1 substantially influence the risk of statin-associated musculoskeletal symptoms (SAMS). The T521C polymorphism (rs4149056) is particularly well-characterized: carriers of the C allele show increased statin myopathy risk, with stronger associations for simvastatin than atorvastatin 2. The Clinical Pharmacogenetics Implementation Consortium now recommends SLCO1B1 genotyping before high-dose simvastatin initiation 1, with dose adjustment strategies varying by statin type 3. SLCO1B1 also transports other cardiovascular and chemotherapeutic drugs, including ACE inhibitors, angiotensin II antagonists, and methotrexate.