Which route of administration involves delivering medication directly into a vein?

The route of administration that involves delivering medication directly into a vein is intravenous administration. This method allows for the rapid onset of action, as the medication is delivered directly into the circulation, bypassing any barriers that other routes may encounter, such as absorption by the gastrointestinal tract or injection into muscle or subcutaneous tissue. Intravenous administration is commonly used in clinical settings for medications that need to be delivered quickly, for high doses, or for those that are poorly absorbed via other routes.

In contrast, the intramuscular route delivers medication into the muscle, where it is absorbed into the bloodstream more slowly than intravenous administration. The subcutaneous route involves injecting medication into the tissue layer between the skin and muscle, which also results in a slower absorption compared to intravenous. The oral route delivers medication through the gastrointestinal tract, where it must undergo digestion and absorption processes before entering the bloodstream, often resulting in delayed onset of action.