Compare and contrast Ametop (amethocaine gel) and EMLA cream. Are there any dangers associated with their use?

EMLA is a significant drug in paediatric practice, but it is commonly prescribed automatically on paediatric wards and applied by the nursing staff. Ametop is a more recent preparation which can be supplied without prescription. This question assesses both basic pharmacological and clinical knowledge of two useful drugs.

Introduction

The introduction of effective topical analgesia to ameliorate the pain of venepuncture has been a very important innovation in paediatric anaesthesia. There are two preparations available: EMLA, which has been available for over 15 years, and Ametop (amethocaine gel), which is a more recent introduction.

Chemistry

Amethocaine (tetracaine)

• Ester linked local anaesthetic.

• Ametop is a 4% formulation produced as a white opalescent gel, containing 40 mg ml–1 of tetracaine (amethocaine) base.

• Onset: application for 30 minutes allows venepuncture; for 45 minutes allows intravenous cannulation.

• Duration: analgesia persists for 4–6 hours after gel removal.

• Produces some vasodilatation.

• Amethocaine is toxic and maximum dose should not be exceeded.

• Is not a prescription only medicine (POM).

EMLA (eutectic mixture of local anaesthetic)

A eutectic (Gk eutektos – ‘easily melting’) mixture is one in which the mixing of two substances of the same consistency produces a mixture of different consistency. This is related to an alteration in the melting point of the mixture: an example is ice and salt, which when mixed produce water.