Four fundamental pharmacokinetic processes—absorption, distribution, metabolism, and excretion—characterize the time course of drug concentrations in the human body. For example, extended-release formulations have a prolonged absorption phase and may modify the parent-metabolite ratio, which can lead to a smoother serum drug concentration curve, maintain the serum drug concentration in the therapeutic range (and thereby limit extreme fluctuations between doses), and alter the potency of the drug. Drug-drug or drug-food interactions and chemical properties (eg, lipophilicity) can also modulate pharmacokinetics. This review summarizes basic pharmacokinetic concepts and demonstrates these concepts using examples of antimuscarinic drugs that treat overactive bladder. The time course of these commonly prescribed drugs is described using these specifically defined and illustrated pharmacokinetic parameters. This review also offers insight into how the knowledge of pharmacokinetics can be applied to better analyze and understand the pharmacologic literature and how this information can be applied to management decisions when treating patients with overactive bladder.