Fig. 1. Sensory function 7 days after intrathecal administration of a commercially available, preservative-free solution of 3% chloroprocaine HCl (Chloro) containing 0.33% NaCl (n = 27); a commercially available solution of 3% chloroprocaine HCl containing 0.18% sodium bisulfite and 0.21% NaCl (n = 26); or preservative-free normal saline (n = 14). Tail-flick latency values were calculated as the average of latencies for the proximal, middle, and distal portions of the tail and are expressed as the percent maximum possible effect (%MPE): ([tail-flick latency − baseline]/[cutoff − baseline]) × 100. Data represent mean ± SEM. *P < 0.05 versus  all other groups.