## **Core Concept**
The maximum permissible dose of lignocaine (lidocaine) is influenced by the presence of adrenaline (epinephrine), which allows for higher doses due to its vasoconstrictive effects, thereby reducing systemic absorption.

## **Why the Correct Answer is Right**
When lignocaine is administered with adrenaline, the vasoconstriction caused by adrenaline decreases the rate of systemic absorption of lignocaine. This allows for a higher dose to be used because peak blood levels are reduced, minimizing the risk of systemic toxicity. The generally recommended maximum dose of lignocaine with adrenaline is **7 mg/kg** or **500 mg**, whichever is less.

## **Why Each Wrong Option is Incorrect**
- **Option A (3 mg/kg):** This dose is lower than what is typically recommended when lignocaine is used with adrenaline, reflecting a dose more suitable for when lignocaine is used without adrenaline.
- **Option B (5 mg/kg):** While closer, this still does not accurately reflect the increased dose that can be administered when lignocaine is combined with adrenaline.
- **Option D (10 mg/kg):** This dose exceeds the recommended maximum for lignocaine even without adrenaline and is not safe for clinical use.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the addition of adrenaline to local anesthetics like lignocaine allows for higher doses to be safely administered due to reduced systemic absorption. This is particularly useful in procedures requiring larger volumes of anesthetic.

## **Correct Answer:** .