Which route of drug administration is associated with 100% bioavailability?

The intravenous route of drug administration is associated with 100% bioavailability because the drug is delivered directly into the bloodstream. This bypasses all barriers that can affect absorption, such as the digestive system and first-pass metabolism that occurs in the liver. As a result, the full dose of the drug reaches systemic circulation and is immediately available for therapeutic effect.

Other administration routes, such as sublingual, intramuscular, or oral, have varying degrees of bioavailability due to factors like absorption efficiency and metabolic processes. For instance, while sublingual administration allows for rapid absorption through the mucous membranes, it does not always achieve complete bioavailability. Similarly, intramuscular injections can have high bioavailability, but absorption can be influenced by factors such as blood flow to the injection site. Oral administration typically has lower bioavailability due to the first-pass effect, where a portion of the drug is metabolized before it reaches systemic circulation.