A Comparison of Amethocaine Cream vs. Liposomal Lidocaine Cream for Venipuncture in Children.

Children commonly require blood taking or placement of an intravenous line for both diagnosis and treatment during their visit to the emergency department. The distress from needle puncture is a particular issue in children. The development of needle phobia can subsequently adversely affect the well-being of the children and their relationship with the medical staff. Thus reduction of pain and distress would be beneficial to patients, parents, and medical personnel.

Amethocaine (tetracaine 4%) (Ametop) is another topical anaesthetic cream which was marketed in Canada over the last 10 years; it was developed by Dr. David Wollfson at Queen's University, Belfast, the cream is available in a 1.5g tube that delivers only 1 dose, at a cost of ($3.24). structurally it has an ester type bond (Para-amino benzoic acid) and is formulated as a free base to allow tetracaine to diffuse across the skin barrier and reach pain receptors (nociceptors) which are located below the stratum corneum (outer most layer of skin). It acts by inhibiting sodium ion flux across the axon membrane thus preventing the nociceptors from signalling pain to the central nervous system. The application time required for the cream is only 30 minutes, and it possesses an action time of 4 hours after removal from the skin. Also Amethocaine has a low risk for methemoglobinemia, therefore it can be used safely in neonatal period and the only disadvantage of Amethocaine cream is skin erythema due to vasodilatation effect.

Liposomal lidocaine 4% cream (Maxilene, RGR Pharma, Windsor, Ontario) is another anaesthetic cream that was launched recently in Canada in 2003. And 5 gm tube priced is 15 $. The liposome-encapsulated formulation protects the anesthetic from being metabolized too quickly (12) It has short onset of action and minimal vasoactive properties that minimize any potential interference with cannulation success, and it is not associated with methemoglobinemia.

As of yet, there has not been a study done in children in the Emergency Department setting comparing the efficacy and side effects of both Liposomal Lidocaine cream and Amethocaine cream. Thus, there is no evidence guiding the use of these agents in Paediatric Emergency care setting, Furthermore using these creams are not considered standard care for children in Canada, and the usual clinical practice in Canadian emergency departments is not to use local anesthesia creams before IV insertion or blood extraction.

Thus, if positive the results of this study could be directly applied to changing the care of children in acute and emergency care setting.

Both creams have shown considerable potential in alleviating procedure pain, but both creams can also cause skin effect, and thus may affect the success rate of these procedures. Therefore we would like to test the two creams to demonstrate the efficacy of these two creams in controlling pain. As Liposomal Lidocaine is believed to have fewer side and skin effects than Amethocaine, it's possible that the success rate may be better with Liposomal Lidocaine than with Amethocaine cream and thus would be preferred agent for use for children in the Emergency and acute care setting.