The Anaesthetic Efficacy of Tetracaine and Oxymetazoline Compared With Co-Phenylcaine in Healthy Individuals

Objectives

Nasal anaesthetic-decongestant sprays are commonly used prior to nasal instrumentation, such as flexible and rigid nasal endoscopy. Co-phenylcaine (lignocaine 5%, phenylephrine 0.5%, ENT Technologies Pty Ltd., Melbourne, VIC, Australia) is a combination spray commonly used for this purpose. However, lignocaine is less potent than other local anaesthetics, and both active constituents of Co-phenylcaine have a bitter taste. It was hypothesised that a combination spray containing tetracaine and oxymetazoline would both offer more potent topical anaesthesia and have a better taste.

Methods

Four anaesthetic-decongestant nasal sprays were tested in 10 healthy participants (Co-phenylcaine, and tetracaine 0.5%, 1% and 2% with oxymetazoline 0.05%). Sensory thresholds were sequentially measured at the head of the inferior turbinate using Semmes-Weinstein monofilaments over the following hour. Participants also rated taste on a Likert-style scale, and reported whether they experienced subjective numbness of the maxillary teeth.

Results

A median peak sensory threshold of 60 g (the maximum tested) was observed with Co-phenylcaine, but this threshold was exceeded by all the tetracaine-based sprays. Tetracaine 2% with oxymetazoline 0.05% had a significantly more rapid onset than Co-phenylcaine (4 min vs. 6 min, p < 0.05) and a longer duration of action. Eight participants reported dental numbness after administration of tetracaine 2% with oxymetazoline 0.05%, but only one participant after Co-phenylcaine. Tetracaine-based sprays were generally perceived to taste less unpleasant than Co-phenylcaine.

Conclusion

Tetracaine 2% with oxymetazoline 0.05% is a more potent and rapidly acting anaesthetic-decongestant spray than Co-phenylcaine, with a longer duration of action.