A nurse is preparing to administer a medication that undergoes extensive first-pass metabolism. What route of administration should be used?
A.
Oral
B.
Intravenous
C.
Subcutaneous
D.
Intramuscular
The Correct Answer and Explanation is :
Correct Answer: B. Intravenous
Explanation:
First-pass metabolism, also known as first-pass effect, refers to the phenomenon where a drug’s concentration is significantly reduced before it reaches the systemic circulation. This occurs primarily in the liver and to a lesser extent in the gastrointestinal tract. The first-pass effect is particularly relevant for drugs administered via the oral route. When a medication is taken orally, it is absorbed through the gastrointestinal tract and then transported to the liver via the portal vein. In the liver, enzymes metabolize a substantial portion of the drug, which can significantly reduce its bioavailability—the fraction of the drug that reaches the systemic circulation in its active form.
Given this background, the most effective route of administration for medications that undergo extensive first-pass metabolism is the intravenous (IV) route. By administering the drug directly into the bloodstream, the IV route bypasses the gastrointestinal tract and the liver’s first-pass metabolism. This ensures that the full dose of the medication reaches systemic circulation and exerts its intended therapeutic effect. This method provides precise control over the dosage and rapid onset of action, making it ideal for drugs that are extensively metabolized by the liver when administered orally.
On the other hand, the oral route (Option A) would lead to significant drug loss due to first-pass metabolism. Subcutaneous (Option C) and intramuscular (Option D) routes do not completely avoid first-pass metabolism but do reduce it compared to oral administration. However, neither of these routes offers the same level of avoidance as the intravenous route. Subcutaneous and intramuscular routes might still result in partial metabolism before the drug enters the systemic circulation, although the extent of first-pass metabolism is less compared to oral administration.
In summary, for medications that undergo extensive first-pass metabolism, the intravenous route is preferred because it avoids the liver’s first-pass effect, ensuring that the full therapeutic dose reaches the systemic circulation.