Final answer:
The route of drug administration with the greatest bioavailability is the intravenous (IV) route, directly entering the bloodstream and providing immediate and complete bioavailability contrasted to other methods.
Step-by-step explanation:
The route of drug administration that produces the greatest bioavailability is intravenous (IV) administration. This method bypasses the gastrointestinal (GI) tract and delivers the drug directly into the bloodstream, providing 100% bioavailability. As shown in pharmacokinetic studies, intravenous administration results in the quickest peak plasma concentration as compared to oral or intramuscular administration, as illustrated graphically in Figure 14.7. This can be significant when treating infections or conditions that require fast therapeutic levels of a drug in the system.
Pharmacokinetics involves the study of how a drug is absorbed, distributed, metabolized, and excreted (ADME), with a key focus on parameters like the area under the drug concentration-time curve (AUC), which represents the drug's bioavailability. Absolute bioavailability (F) measures the extent and rate at which the drug enters systemic circulation, thereby reaching the intended action site. Given the direct delivery of the medication into the bloodstream, intravenous administration diminishes the impact of factors such as metabolism by drug-metabolizing enzymes like UGT and the presence of drug transport proteins like BCRP, which can affect oral bioavailability.