Which route of administration has the shortest duration for acetaminophen?

The correct answer is the intravenous (IV) route of administration. The intravenous route allows for rapid delivery of acetaminophen directly into the bloodstream, leading to immediate therapeutic effects. When administered IV, acetaminophen reaches peak plasma concentrations quickly, resulting in a shorter duration of action compared to other methods.

In contrast, oral administration requires the drug to be absorbed through the gastrointestinal tract, which can take longer to achieve therapeutic levels. Rectal administration also involves absorption through the rectal mucosa, which may vary in speed and consistency. Subcutaneous administration involves injecting the drug into the fatty tissue, which typically leads to slower absorption and therefore a longer duration of action.

Overall, the intravenous route provides the fastest onset of action and shortest duration due to its direct access to the circulatory system, making it the optimal choice for immediate pain relief.