Mechanistic modeling of drug behavior and response is essential for rational drug development and personalized therapy, yet constructing, maintaining, reusing and customizing complex pharmacokinetic–pharmacodynamic and physiologically based pharmacokinetic models can be error-prone when implemented solely via equations or code. We introduce Pharmacolibrary, a free Modelica library offering standardized acausal components for pharmacokinetics, pharmacodynamics, toxicokinetics/toxicodynamics and pharmacogenomics from compartmental and physiologically based templates to effect models and genotype–phenotype records—to simplify model reuse, customization, and interoperability. Its utility is showcased with gentamicin, midazolam, and fentanyl case studies, including pharmacogenomics-driven clearance adjustments and pharmacodynamics simulations.