Modification of pain on injection of propofol--a comparison between lignocaine and procaine. Pain on injection of propofol was assessed in a controlled, randomised study of 273 patients. They received either lignocaine 10 mg, procaine 10 mg or isotonic saline 0.5 ml, 15 seconds before the injection of propofol into a vein on the back of the hand. The incidence of pain on injection in the control group (51%) was comparable with other studies. Lignocaine and procaine both significantly reduced the pain (35% and 34% respectively, p less than 0.05) but there was no statistical difference between these two groups. 