ANTINOCICEPTION PRODUCED BY SPINAL DELIVERY OF THE S AND R ENANTIOMERS OF FLURBIPROFEN IN THE FORMALIN TEST

The antinociceptive effect of spinally delivered S- and R-flurbiprofen , enantiomers of 2-arylpropionic acid, was studied in rats using the f ormalin test. Intrathecal injections of S- or R-flurbiprofen produced a significant reduction of the second phase of the formalin test, with no effect on the first phase. The maximal suppression of the second p hase was similar for both agents (about 50% at the highest doses). Whi le both agents were active, S-flurbiprofen was significantly more pote nt than R-flurbiprofen. The potency ratio between the dose-response cu rves was 10 (6-20; 95% confidence intervals). These results demonstrat e that both S- and R-flurbiprofen produce antinociception after spinal administration. The potency difference is similar to that for inhibit ion of cyclooxygenase in brain tissue and supports the hypothesis that cyclooxygenase products are involved in prolonged spinal nociceptive transmission.