**Question:** Which of the following has the shortest plasma half-life?

A. Digoxin
B. Morphine
C. Dexamethasone
D. Warfarin

**Core Concept:** Plasma half-life is a measure of how quickly a substance is eliminated from the body. It is determined by the rate at which the substance is broken down or excreted. A shorter half-life indicates that the substance is more rapidly cleared from the bloodstream.

**Why the Correct Answer is Right:** Dexamethasone has a short plasma half-life of approximately 30-60 minutes. This is due to its strong glucocorticoid effects and its ability to induce rapid cellular uptake and organ storage. Since it is rapidly broken down and eliminated, its effects are short-lived, making dexamethasone's plasma half-life the shortest among the given options.

**Why Each Wrong Option is Incorrect:**

A. Digoxin (0.5-2 hours) and Warfarin (4-20 hours) have longer plasma half-lives, indicating that they are more slowly broken down and eliminated from the body.

B. Morphine (2-6 hours) has a longer plasma half-life compared to dexamethasone, making it the incorrect answer.

**Why Each Wrong Option is Incorrect:**

C. Dexamethasone (30-60 minutes) has the shortest plasma half-life among the given options.

**Clinical Pearl:** A short plasma half-life of a medication can lead to inadequate therapeutic effects if not dosed appropriately. On the other hand, a very short half-life can result in frequent dosing and potential side effects. Therefore, understanding the plasma half-life of a medication is crucial for appropriate dosing and patient care.