Answer
It narrows nearby blood vessels, reducing bleeding and slowing lidocaine absorption so its local effect lasts longer.
Sources for this answer
- Lidocaine 10 mg/ml (1% w/v) with Adrenaline (Epinephrine) 1:200 000 solution for injection — Current selected SmPCemc · Summary of Product Characteristics
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.