Despite use of colour-coded labels, syringe substitution (syringe swap) error of anaesthetic drugs remains a frequent and potentially serious cause of iatrogenic harm. We explored the novel concept of using a simple device which can be fitted to existing syringes, and employs colour and raised elements (detents) to provide visual, haptic and auditory cues to supplement the visual cues provided by standard drug labelling, and particularly helps to differentiate, for example, syringes containing vaso-active drugs from other syringes. We produced six different embodiments of the device, and performed a randomised unblinded study with 14 volunteers to identify the functional characteristics which met with the approval of the majority of participants, and the mechanical characteristics which produced adequate haptic feedback without excessive resistance to injection. The optimal design was identified, which required the user to exert a mean (SD) force of ~20 (7) N to overcome the resistance of the detents in the syringe. The majority of volunteers felt that a device of this type would be helpful in reducing the incidence of syringe substitution error; however, further research is needed to assess the efficacy of this innovation in the clinical environment.