Tetracaine gel 4% is a topical anaesthetic gel commonly used in the UK that contains 40 mg of tetracaine base per gram. Adequate anaesthesia can usually be achieved following a 30 minute application time for venopuncture and a 45 minute application time for venous cannulation. The hypothesis is that Rapydan medicated plaster is more effective than tetracaine gel in preventing venous cannulation related pain when applied for the recommended treatment durations of 30 minutes and 45 minutes respectively.