Understanding the role of pharmacodynamics in determining a drug's effect helps prescribing physicians choose the most appropriate agent and regimen to achieve the optimal balance of beneficial and adverse effects. The pharmacodynamic profile describes how a drug exerts its effects on the body, whether by physical, chemical, or enzymatic activity, or through receptor interaction at a cellular level. Drug-receptor binding results in biologic and physiologic effects, while the nature of binding defines the drug activity and dose-response relationship. Muscarinic receptor antagonists (antimuscarinics) are used in the treatment of overactive bladder. Antimuscarinics competitively block acetylcholine binding to muscarinic receptors in the detrusor smooth muscle and urothelium/suburothelium of the bladder. To make pharmacodynamic principles more relevant to the clinical urologist, this review summarizes clinical pharmacodynamic concepts, using the current antimuscarinics prescribed for overactive bladder and other urologic disorders as examples.