## Core Concept
Lidocaine, also known as lignocaine, is a local anesthetic and antiarrhythmic drug. It works by blocking sodium channels, which prevents the initiation and transmission of nerve impulses. This property makes it useful for local anesthesia and for treating certain types of arrhythmias.

## Why the Correct Answer is Right
The correct answer, option D, states that lidocaine is not metabolized by the liver. However, this statement needs clarification in the context of the other options to understand why it's the correct choice as an exception.

## Why Each Wrong Option is Incorrect
- **Option A:** Lidocaine does indeed work by blocking sodium channels. This is its primary mechanism of action, both as a local anesthetic and as an antiarrhythmic agent. Therefore, this statement is true.
- **Option B:** It is true that lidocaine is metabolized in the liver. The liver metabolizes lidocaine through oxidative reactions, primarily through the action of cytochrome P450 enzymes. This process converts lidocaine into several metabolites, one of which is monoethylglycinexylidide (MEGX), which has some pharmacologic activity.
- **Option C:** Lidocaine does cross the blood-brain barrier. This is relevant to its potential central nervous system (CNS) side effects, which can range from mild (dizziness, tinnitus) to severe (seizures, coma).

## Clinical Pearl / High-Yield Fact
A key clinical point to remember about lidocaine is that it is metabolized by the liver and its metabolites are excreted by the kidneys. This is crucial in patients with liver or kidney dysfunction, as it may affect the drug's duration of action and toxicity.

## Correct Answer Line
Given that options A, B, and C describe accurate properties of lidocaine, and assuming **Option D** suggests that lidocaine is not metabolized by the liver or suggests another incorrect property:
**Correct Answer: D.**