## **Core Concept**
The question tests knowledge of local anesthetic dosing, specifically the maximum safe dose of lignocaine (lidocaine) when used with adrenaline (epinephrine). Lignocaine is a commonly used local anesthetic, and its maximum dose can be increased when combined with adrenaline due to the vasoconstrictive effects of adrenaline, which decrease systemic absorption.

## **Why the Correct Answer is Right**
The addition of adrenaline to lignocaine allows for a higher maximum dose because adrenaline causes vasoconstriction at the site of injection. This vasoconstriction reduces the rate of systemic absorption of lignocaine, thereby decreasing its systemic toxicity. The generally recommended maximum dose of lignocaine with adrenaline is up to **7 mg/kg**, with a maximum total dose often capped at 500 mg. This increase in the safe dose is crucial for procedures requiring larger volumes of anesthetic.

## **Why Each Wrong Option is Incorrect**
- **Option A (3 mg/kg):** This dose is too low for lignocaine with adrenaline. It's more reflective of the maximum dose without adrenaline.
- **Option B (4 mg/kg):** Still lower than the recommended dose with adrenaline, possibly reflecting a dose without adrenaline or a very conservative estimate.
- **Option D (10 mg/kg):** This is higher than the generally recommended maximum dose for lignocaine with adrenaline and could increase the risk of systemic toxicity.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the addition of adrenaline to local anesthetics like lignocaine doubles the safe dose from **4 mg/kg** (without adrenaline) to **7 mg/kg** (with adrenaline), making it a critical consideration for safe and effective local anesthesia.

## **Correct Answer:** C. 7 mg/kg.