During this period, molecular and biochemical methods dominated pharmacology, linking drug effects to precise targets such as enzymes and receptors. The field integrated quantitative kinetics, receptor identification, and neurotransmitter biology to explain drug actions, enabling targeted therapeutic strategies. The methodological shift laid the groundwork for molecular pharmacology as a distinct, mechanism-driven discipline. Historical Significance: The era produced defining breakthroughs that shaped downstream research, including a concise framework for characterizing enzyme inhibitors, early classification of adrenergic receptors, and new insights into cholinergic transmission and brain catecholamine metabolism. Collectively these advances unified pharmacology around molecular targets and mechanistic explanations for drug action, guiding future drug design and research directions.