Pharmacy PEBC Practice Exam

What does the "first-pass effect" refer to?

1. The elimination of drugs from the body

2. Metabolism of a drug before systemic circulation

3. The initial absorption of a drug into the bloodstream

4. The interaction of drugs with food in the stomach

The correct answer is: Metabolism of a drug before systemic circulation

The first-pass effect refers to the metabolism of a drug before it reaches systemic circulation. When a drug is administered orally, it is absorbed through the gastrointestinal tract and then transported via the bloodstream to the liver through the portal vein. In the liver, the drug can be metabolized significantly before it enters the general circulation. This extensive metabolism can reduce the concentration of the active drug that reaches the systemic circulation, which is a critical factor in determining the bioavailability of many medications. Understanding the first-pass effect is essential for predicting the therapeutic efficacy of orally administered drugs, as it can lead to a diminished pharmacological effect if the drug is extensively metabolized. This concept highlights the importance of considering both the route of administration and the biochemical processes that occur before a drug exerts its effects in the body.