## **Core Concept**
Thiopentone, also known as thiopental, is a barbiturate used for the induction of general anesthesia. It acts rapidly to induce unconsciousness. The typical formulation of thiopentone for clinical use is a powder that needs to be reconstituted.

## **Why the Correct Answer is Right**
The correct answer, **1%**, is the commonly used concentration for thiopentone induction. When reconstituted, a 1% solution of thiopentone sodium is isotonic and has a pH close to physiological pH, making it suitable for intravenous administration. This concentration allows for the rapid delivery of the drug to the brain, facilitating quick induction of anesthesia.

## **Why Each Wrong Option is Incorrect**
- **Option A: 0.5%** - While lower concentrations could theoretically be used, they are less practical for rapid induction of anesthesia as more volume would be required to achieve the desired effect, potentially leading to slower onset times.
- **Option B: 2%** - A 2% solution is higher than the standard concentration and could increase the risk of local tissue irritation or complications upon injection, without providing significant benefits in terms of onset or recovery.
- **Option D: 5%** - A 5% solution is much higher than the standard and would likely cause significant local irritation and increase the risk of thrombophlebitis, making it impractical for routine use.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that thiopentone is usually prepared as a 1% solution (10 mg/mL) for induction of anesthesia. This concentration helps in achieving a rapid and smooth induction with minimal side effects. Always verify the concentration of the solution before administration to ensure patient safety.

## **Correct Answer:** C. 1%