Which is an example of a medication that does not undergo extensive first-pass metabolism?

The correct answer identifies intravenous medications as examples that do not undergo extensive first-pass metabolism. First-pass metabolism occurs when a drug is metabolized in the liver before it reaches systemic circulation. This primarily affects medications that are administered via the oral route, where the drug goes through the gastrointestinal tract and then is processed by the liver before entering the bloodstream.

Intravenous medications, on the other hand, are administered directly into the bloodstream. Since they bypass the gastrointestinal tract and the liver during this initial phase, they do not undergo first-pass metabolism, allowing for 100% bioavailability. This means that the full effect of the drug is available for therapeutic action without being significantly altered or reduced by metabolic processes.

Topical and subcutaneous medications can also undergo varying degrees of metabolism; however, the extent and impact on overall bioavailability differ. Topical medications may reach systemic circulation if they are absorbed through the skin, but they are usually designed to act locally. Subcutaneous medications also enter the bloodstream but will still have some degree of first-pass metabolism depending on how much reaches the liver before systemic circulation, which is not the case with intravenous administration.