**Question:** Eutectic mixture of local anaesthetic (EMLA) cream is:

A. Lidocaine and prilocaine
B. Lidocaine and bupivacaine
C. Lidocaine and ropivacaine
D. Lidocaine and mepivacaine

**Correct Answer:** A. Lidocaine and prilocaine

**Core Concept:**
EMLA cream is a topical anaesthetic used for pain relief during venepuncture or minor skin procedures. It is a eutectic mixture of two local anaesthetics: lidocaine and prilocaine. The eutectic mixture means that the two substances have a lower freezing point than when they are separated, allowing the cream to remain liquid at room temperature.

**Why the Correct Answer is Right:**
Lidocaine is a commonly used local anaesthetic with fast onset and short duration of action, while prilocaine has a longer duration of action and is less likely to cause systemic toxicity. Combining these two agents in a eutectic mixture allows for a synergistic effect, enhancing the duration and effectiveness of local anaesthesia while reducing the risk of systemic toxicity.

**Why Each Wrong Option is Incorrect:**

**B. Lidocaine and bupivacaine:**
Bupivacaine is a long-acting local anaesthetic with a risk of systemic toxicity. Using bupivacaine in EMLA cream would decrease the effectiveness of the local anaesthetic and increase the risk of systemic toxicity.

**C. Lidocaine and ropivacaine:**
Ropivacaine is a long-acting local anaesthetic similar to bupivacaine, which would also decrease the effectiveness of the local anaesthetic and increase the risk of systemic toxicity.

**D. Lidocaine and mepivacaine:**
Mepivacaine is a local anaesthetic with a similar duration of action to lidocaine, making it a less effective combination for achieving longer anaesthesia and increasing the risk of systemic toxicity.

**Clinical Pearl:**
EMLA cream is an effective and safe alternative to injectable anaesthesia for minor skin procedures and venepuncture, as it reduces the risk of pain during the procedure and prevents the need for injectable anaesthesia. This minimizes patient discomfort and potential complications associated with injectable anaesthesia.