Which of the following local anaesthetic is safer in surface and infiltrating anaesthesia?
**Core Concept**
Local anaesthetics are categorized based on their pharmacological properties, including their lipid solubility, pKa, and ability to cross biological membranes. The choice of local anaesthetic depends on the specific application, such as surface or infiltrating anaesthesia, where the goal is to minimize toxicity while maintaining efficacy.
**Why the Correct Answer is Right**
The correct answer is **Articaine**. Articaine is a local anaesthetic with a lower systemic toxicity profile compared to other local anaesthetics, making it safer for surface and infiltrating anaesthesia. Its lower lipid solubility and higher protein binding capacity contribute to its reduced toxicity. Additionally, articaine has a rapid onset of action and a short duration of action, which is beneficial for surface anaesthesia.
**Why Each Wrong Option is Incorrect**
* **Option A:** Lidocaine is a widely used local anaesthetic, but it has a higher systemic toxicity profile compared to articaine, making it less suitable for surface and infiltrating anaesthesia.
* **Option B:** Bupivacaine is a long-acting local anaesthetic with a high lipid solubility, which increases its risk of toxicity, especially when used for surface and infiltrating anaesthesia.
* **Option D:** Mepivacaine is another local anaesthetic with a higher systemic toxicity profile compared to articaine, making it less suitable for surface and infiltrating anaesthesia.
**Clinical Pearl / High-Yield Fact**
When choosing a local anaesthetic for surface and infiltrating anaesthesia, it's essential to consider the agent's lipid solubility, pKa, and ability to cross biological membranes to minimize toxicity while maintaining efficacy.
**Correct Answer:** C. Articaine