**Core Concept**
Flumazenil is a benzodiazepine receptor antagonist used to reverse benzodiazepine-induced sedation, anesthesia, and muscle relaxation. Its duration of action is an essential pharmacokinetic property that influences the timing and efficacy of reversal.

**Why the Correct Answer is Right**
Flumazenil's duration of action is approximately 1-2 hours, which allows for effective reversal of benzodiazepine effects while minimizing the risk of prolonged sedation or rebound anxiety. This duration is a result of flumazenil's pharmacokinetics, including its rapid onset of action (typically within 1-2 minutes) and relatively short elimination half-life. Flumazenil is metabolized by the liver and excreted in the urine, with a clearance rate that contributes to its short duration of action.

**Why Each Wrong Option is Incorrect**
**Option A:** 5 minutes is an overly short duration for flumazenil's action, as it would not provide sufficient time for effective reversal of benzodiazepine effects.
**Option B:** 10 minutes is still too short, as flumazenil's action typically lasts longer than this timeframe.
**Option C:** 20 minutes may seem plausible, but it underestimates the actual duration of flumazenil's action.

**Clinical Pearl / High-Yield Fact**
Flumazenil's short duration of action requires careful monitoring and repeated dosing to ensure complete reversal of benzodiazepine effects, particularly in patients receiving high doses or with compromised liver function.

**✓ Correct Answer: D. 1-2 hours**