Effect of 1.5% diclofenac on temporal pain summation. A scattered plot illustrating quantitative sensory testing responses to a train-of-four identical suprathreshold heat (47°C) stimuli after application of diclofenac lotion or placebo. Delta 1, delta 2, and delta 3 represent the percent increase in visual analog scale score in response to the second, third, and fourth stimulus over that to the first stimulus, respectively. *P = 0.01, as compared between 1.5% diclofenac group and placebo solution group.