Which route of administration has the shortest duration of action?

The intravenous (IV) route of administration has the shortest duration of action primarily because it delivers the drug directly into the bloodstream, allowing for rapid onset and clearance. This method bypasses absorption barriers found in other routes, such as the gastrointestinal tract for oral medications or the layers of muscle and subcutaneous tissue for IM or SC injections.

Once administered via IV, the drug quickly reaches systemic circulation, where it can exert its therapeutic effects almost immediately. However, due to the nature of IV administration, particularly for drugs with short half-lives, the duration of action tends to be brief. As the drug is metabolized or eliminated by the body, the effects diminish quickly, necessitating either continuous infusion or repeated dosing to maintain therapeutic levels.

In contrast, oral administration typically involves absorption through the gastrointestinal tract, leading to a delayed onset and prolonged action as the drug is distributed and slowly released into the bloodstream. Subcutaneous and intramuscular routes also involve tissue absorption, which can further extend the duration of action compared to IV administration.