**Core Concept:** Local anaesthetics are a class of drugs that inhibit voltage-gated sodium channels, resulting in loss of sensation and motor function in a specific area. They are widely used for regional anaesthesia and pain management. The duration of action depends on the chemical structure and lipophilicity of the drug. Longer-acting agents are more lipophilic and cross the blood-brain barrier, affecting systemic toxicity.

**Why the Correct Answer is Right:** D-Lignocaine (Lidocaine) is a widely used local anaesthetic drug with a longer duration of action compared to other options due to its lipophilic nature. It is a tertiary amine and has a higher affinity for fatty tissues, allowing it to cross the blood-brain barrier and prolong its action.

**Why Each Wrong Option is Incorrect:**
A. Levobupivacaine: This is a lipophilic local anaesthetic drug, but its duration of action is shorter than lidocaine.
B. Ropivacaine: Another lipophilic local anaesthetic drug, but its duration of action is shorter than lidocaine.
C. Bupivacaine: This drug is lipophilic but has a shorter duration of action compared to lidocaine.

**Clinical Pearl:** Prolonged use of long-acting local anaesthetics can lead to cardiac toxicity, neurotoxicity, and a higher risk of seizures due to their systemic spread. Therefore, careful dose selection and monitoring are essential when using these drugs.

**Correct Answer:** D-Lignocaine (Lidocaine)