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.